Fans are great and a must, because they increase airflow.
But, there is one thing, poor quality fans produce noise and are loud... you know.. really loud. Use your imagination, and invest a couple of bucks: buy 120mm Artic Cooling fans (they are awesome, I personally use 2 of those)-- 120mm fans move more out, their cfm is a lot
higher than 80mm ones, and because their spinners are larger, they don't need to rotate at thousands of rpm, unlike 3000-4000rpm (as 80mm's do), they rotate around 1500-2000rpm, and this reduced the amount of noise. Then of course, quality is again a terrific factor. Artic Cooling, xFlow, Zalman, Scythe, Thermaltake are some of the most reputated companies, their product is awesome and quiet. Of course, you can also oil your fan(s). It's going to reduce the noise, because they are going to spin easier.
So summing it up a bit, computers are tools, they are working for us, doing our job, or we game on them, so whatever we do, we put stress/load on them. They will
warm up, becoming hot, and the processor (along with video card, mems, chipsets, etcetera) they must be cooled down. Otherwise overheating can
produce instabilities, even can degrade component's lifespan dramatically. So you must have fans around. A great and typical airflow setup is something like 1x120mm fan at the rear of your case, to exhaust air. Another 1x120mm fan at the front of your case to intake fresh air. Then the a 80mm (or if possible 120mm) fan on the side panel to intake fresh air directly on the air trought an air duct (which is commonly used nowaday on every computer case). PSU fan is not enough to move air, because it's going to exhaust the hot air generated by the Power Supply Unit itself (most of the cases). Low quality PSUs also have poor quality fans, and they're going to be loud and noisey, so oiling it will help again here.
Then again, choosing an aftermarket cooling for your CPU helps keeping your temperature lower, and also reduces the amount of noise generated dramatically. Look forward for Zalman CNPS products (7000cu, 9500), Artic Cooling Freezer 64/7 Pro, Scythe KATANA-cu, Thermaltake Big Typhoon. Or you could also do yourself a CPU cooler- by getting yourself a high quality heatsink: something like Thermalright XP-90, XP-120, then stick a quality 90mm/120mm fan on it, it's going to be awesome. Also, whenever if you decide to stay with your stock cooler or aftermarket, you should replace your thermal compound. Thermal compound usually used for stock coolers/heatsinks are poor quality. Get Artic Silver 5, it's a must, trust me on this. It's going to reduce your load temps with ~5C (min) up to ~12C (in some cases). There are just way too many guides over the net on how to apply thermal paste's, so this shouldn't let you down. It's very easy. Take off your heatsink, clean up your original thermal grease (with some sort of alcohol, there are a lot of alternatives, thing is that it's needed to evaporate fast), then apply one very thin layer of AS5 with a razor blade or credit card, or anything. Then seat the heatsink on it carefully, make sure it's going to make direct contact with your CPU. Then as soon as you boot up, put some serious load on your system: stress test, calculate pi, render something, encode some music, archive some files, game your favoruite game, do anything for a hour or so, this is must to let your thermal compound melt. Then you're set up. You are
going to notice a huge difference. Artic Silver 5 is one of the best (if not the best) thermal compound currently on the market, and I'm sure you can afford the little tube of 3.5mg one, it's around 6$ only.
As a side note, if you want extremely quiet system, and money is not a problem, then of course, there are a lot of premade water cooling kits
, which are easy to set up, everybody can do it. Usually these are couple hundreds of us dollars anyway, but they are worth. Zalman Reservoir, Thermaltake Big Water, Scythe, Danger Den's... etc are awesome quality ones. If you decide to go with water cooling, please, do not skimp on their price. Just because one is 300$ and the other one is 100$, that doesn't means that the 300$ one is overkill, it only means that the 100$ one is of poor quality, and you could easily end up with a defective pump or a leaking, or you name it. Before making your final decision, read a few reviews to decide if it's worth or not.