Are specifications of Motherboard important?

Are specifications of Motherboard important?

1. FSB / RAM speed limits
In motherboard specifications, it will specify the max FSB and RAM speed support (eg 1333 FSB and DDR2 667). Nevertheless, as long as the motherboard supports overclocking, it appears I can overclock FSB more than 1333 and RAM more than 800.

So what do all those figures really mean? What are they really for if I can simply ignore the figures and pass the limits?

If I buy a DDR2 800 RAM, am I able to use in a motherboard which says to support DDR2 667 only? If so, how will the RAM run (being underclocked to 667??) ?

What if I overclock the RAM, am I able to let my RAM run at a speed higher than 667?


2. 3 or more monitors
If I want to use 3+ monitors, I believe I need 2 graphic cards, isn't it? If so, do I need a motherboard with two PCIe x16 slots to install 2 graphic cards? What about other PCIe slots like PCIe x1 slots?

3. PCIe x1
What's the use of PCIe x1 slots? Are PCIe x1 cards common? Are they cheaper or dearer than the older PCI cards?
I would like to get a modem card (to fax with my computer) and Ethernet card. Should I go for old PCI or the new PCIe?

4. RAM compatibility list
I'm a bit worried that the RAM I purchase can't work nicely with my motherboard. I wonder if I should strictly limit my choices to those which are in my motherboard "RAM compatibility list".

Question about RAM model number: Take A-Data DDR2 800 for example, there are several models available even for the same RAM speed. Will there be cases where a model from brand A can cause compatibility problems while another model from brand B won't? I just wonder if I should take the model number into account when I try to pick a compatible RAM for my motherboard.


My PC Info which may be helpful:
CPU: Intel E2180
RAM: 2GB or 2GBx2; DDR2 667 or 800
Motherboard: not decided yet. Socket LGA 775
HDD: Western Digital WD6400AAKS (640GB, SATA2)
Display card: not decided yet. Perhaps HD2600Pro
Monitor: not decided yet. Two cheap 1680x1050 monitors

Yes, they're all important. Most manufacturers set limits based upon overall safe and consistent operation. Overclocking usually is the extra (as much as 20% for some CPU's) wiggle room they use a test basis for max stress. Motherboards are similar in a lot of ways. Though its kinda hard to screw RAM up...if you throw too much or the wrong frequency, the most likely incident you'll have is the system not booting amidst much beeping, pissing and moaning from the board itself. You can tweak the hell out of them, but I wouldn't advise getting too crazy. Remember experimentation is part of the fun. Just keep this in mind though, unless you have deep pockets to buy redundant hardware, I'd keep things within reason.
On the 3 monitors, yea you'll need two one with a DVI and VGA out (you'll need a DVI-to-VGA converter obviously to have two of the 3 VGAs), then a second card with just one VGA out will suffice. I'd spend a little extra cash and get a card with some muscle for the one you run the duals from. Try to get the same type card if you can. Makes things a bit simpler to manage. Most good video card soft supports this (Nvidia and ATI)...I prefer Nvidia stuff myself ,but its really just whatever you like.