well these days pretty much any mainstream video card will be sporting dual DVI, and support up to 2x 2560x1600 displays. So really anything in the HD2600 or Geforce 8500 series, or above will work just fine got actually displaying the images. If you are looking for something that will support 1680x1050 for gaming, or dual 1680x1050 for gaming, then you need something with a bit more power. Cards in the Nvidia Geforce 9600 series or the ATI HD 3850 series will do just fine for single 1680x1050 gaming. Dual monitor gaming will require higher end hardware in the ATI HD 4850 or Nvidia 9800 series.
As for specific make and model, it really wont make a big difference. Really what will separate them will be brand name, cooling, and quality. Brand name is kind of important, some companies will offer better services than others, such as EVGA or XFX. EVGA has a good "step up" program, where in they will refund you your entire invoice price towards a faster video card. Or XFX, who offer a double lifetime warranty, allowing you to register the card yourself, and even if you sell it to someone else they will get a full lifetime warranty as well. Stuff like this is helpful to you, and if you were to sell the card.
Cooling is pretty simple, you can get cards with the reference cooling design, a very straight forward design, small heatsink and fan combo. Some makes will have larger heatsinks an fan(s), others may just use a large heatsink and no fan. All of this can impact noise levels and temperature levels. If you want a quieter computer, larger heatsinks with slower fans will do that, or a passively cooled model with no fan will be ideal. If you live in an area that is always hot and humid, this may not be an option for you and you may have to go with a well equipped model. If you live in a cold climate then the cooling wont matter all that much... I live in texas so I gotta go big
Quality is the final category. Some card makers will offer higher quality components on board, such as better quality memory, more memory, or factory overclocked settings. Things like this can impact performance and further overclockability. Cards with larger coolers and superior memory are going to (typically) allow you to overclock further than cards equipped with weaker coolers and cheaper memory. You also factor in things like bundle, some cards will come with games or software, others will not.
So its really a matter of looking at what you really need. If a basic card is all you need you can save yourself a good chunk of change by going with just that basic card. The same model card can be $50+ in price just because it has a better heatsink and comes with a copy of Call of Duty 4. That may not matter to you, so why spend more than you have too?
As for the LCD, its about popularity as well. Right now the standard for gamers is the 1680x1050 20-22" widescreen. 1600x1200 4:3 units are more popular in business settings than gaming, so the prices reflect that. The more competitive market is 1680x1050 and a lot of people prefer having a widescreen. These days most games will support widescreen resolutions so it wont be a problem in that respect. As for sheer number of pixels you can simply do the math, 1600x1200=1,920,000 pixels, 1680x1050=1,764,000 pixels. So yes, 1600x1200 is slightly more pixels, but 1680x1040 is widescreen, so you will get a better field of view in games that support wide screen.
Brightness, contrast, and response time do matter, but you are correct that its not the be-all end all because you will really never notice much of a difference unless you have 2 models side by side. Brightness and contrast are more noticeable and will effect color accuracy to a certain extent, and this is important because the can be the difference between bright, vivid colors, and dull washed out colors. Proper tweaking and tuning will help improve things. Response time is also important to avoid tearing in your games specifically. This is less of a problem today and even keeping under 16ms true response time is fine. You can use vsync option with your card or games to combat the problem of tearing. Lower response times will help a lot there, but the days of 30ms response time are long gone and as it is today only highest resolution displays really have any trouble.
durability to me really only means 1 thing...the stand. I dont haul my 24" screen to lan parties or pack it up back in its box every night, so the important thing for me was a fully adjustable stand. I like my Dell 2407 because its stand is height adjustable, pan, tilt, and I can rotate it 90 degrees so I can have a portrait mode for reading large amounts of text (such as this rant here :P). Cheaper units use cheaper stands, its pretty simple. Some wont even offer height adjustments, the cheap ones only offer minor pan & tilt.
ports and connectivity is all up to you. If the monitor has DVI, and your pc has DVI, then it'll plug in fine. If you have a need for something other than DVI, make your choice with that factored in. My monitor for example has component and composite connections, so i can hook up an xbox or such things and use my 24" monitor as a display for that. Or if I had HDMI I could use that to hook up a dvd/HD player to my monitor and use that as a display for my movies. A nice thing about my dell that I use often is the DVI connection is hooked to my main pc, and the VGA connection is hooked to my benchmarking pc, so while I am working on my reviews, all I have to do is hit 1 button to switch between the two inputs, so I can be running my tests at 1920x1200 without having to buy a second monitor
Other monitor features like card readers or USB ports are also gunna depend on your needs. I couldnt live without mine, I dont have a card reader for my compact flash cards because I have one built into my monitor. So once I take my photos on my D100, I pop out the card, plug it into the card reader in the monitor, and off I go. It saves me from having a usb one that I may lose on my desk, or a drive bay model that would ruin the look of my case.
USB is also nice for me because I can plug my keyboard and mouse into the monitor (or external hard drives and such) and keep my cables nice and tidy, and only have to have 1 USB cable going into my pc...the one that connects the monitor USB hub to the pc. This is handy of you dont have front mounted USB ports on your case, or if you need to have easy access to the ports for things like external hard drives.
hope that helps...