First you need to figure out the primary source of noise that you need to quiet down.
CPU fan
GPU fan
Case fan(s)
PSU fan
Which is it?
Open the case, and stick a pencil in each fan for a few seconds. See which one makes the most difference. If you remove the noise from only ONE source, does it become a tolerable noise level?
I ask this primarily because I've seen friends try to quiet systems down with cheap components like you're suggesting and they generally come away disappointed. The key to real silence is efficiency, and ultimately that costs money. Find the main contributor and fix it RIGHT.
There is a review for that Heatsink here:
http://www.frostytech.com/articleview.cfm?articleid=2539&page=5
at low speed it's comparable to a stock Intel HSF, though a little quieter (not a ton though). At high speed it's okay, but only if you are height restricted.
you have a PWM header on your board, so you should want a PWM fan for your cooler, this will let you tune the airflow (and noise) very well.
I use a Xigmatek S1283 plus the optional screw mounting kit. While this is considerably more expensive, look at the OCZ Vendetta 2 in the Frostytech chart, this is essentially a re-labeled 1283 with a quieter fan. Fan noise is a little over 1dB higher, temps are 10C lower on the 150W test. Not only that, but I bought it for my Socket 775, and when Intel changed the heatsink config for 1156, I was able to just get a mounting bracket and move it on over. It has the kind of cooling that does not compromise overclock performance much to be silent (assuming you use the PWM control to turn the fan down, since it is not a silent fan at full blast).
I don't see spending money to get a heatsink that is about as good as the Intel cooler, but a tad bit quieter as a good value at any price.
Coolermaster Hyper 212 is a similar cooler with high value:
http://www.amazon.com/Cooler-Master-RR-B10-212P-G1-Universal-Heat-Pipe/dp/B002G1YPH0
Some people have issues with this one and DRAM slots. I don't have personal experience with it, but it's very similar to the S1283 in most respects and has a PWM fan as well.
- If it's your video card, I suggest an Arctic Cooling Accelero S1 Rev 2.
http://www.svc.com/fan-acces1.html
Consistent performer that will cool anything if you zip tie a fan to it. Cheap and easy. Takes up a ton of slots, but most people don't have a bunch of cards anymore. I wouldn't run it passive on most cards, but it doesn't need much airflow at all. I ran one on my 4850 with an undervolted fan on it, it was completely silent and was running a 100 MHz overclock. Center the fan over the VRM heatsink, which also puts it over 2 of the heatpipes.
- If it's your case fans, first try your existing fans undervolted. 4-pin Molex connector is 12v yellow, 5v red, ground black. Fan wires are usually red and black. They'll be wired to yellow and black on the 4-pin connector. Try it on 5v instead of 12v. This works for some fans, but many it's too low a voltage. 7v usually works great though (red fan wire to the yellow 12v, black fan wire to the red 5v). Totally free and worth it to try.
silentpcreview.com is a good source for fan reviews. They also run fans at various voltages so you can see performance when undervolted. Xbitlabs also has very complete fan roundups. Generally depends on your other choices. You usually want to select fans from wherever you're getting other stuff just due to shipping costs, and nobody sells every fan.
- Most PSUs are pretty quiet these days, I'd be surprised if it's your PSU. I don't have a good recommend here, because I don't have a lot of experience with PSUs.
Wiring-wise, most fans will connect via the mobo header, or via the 4-pin molex connectors. A PWM controlled fan is useful if you have a 4-pin header on the motherboard.
There are y-connectors for PWM fans:
http://www.svc.com/fc444pwm-12.html
If you have a choice between exhaust and intake fans, I prefer exhaust, but others think opposite. If trying to keep things quiet, I'd choose only one. If you go with the Accelero, you probably won't have room for a side case fan.
These options do cost more, but I would really suggest not doing as you originally plan. You might dent the sound from your case enough, but it won't last. Find your primary offender and hammer it into submission, then later address another area when you have the money. The cheap approach leaves you with a pretty quiet system at stock speeds if you have enough airflow through your case. The other approach leaves you with a pretty quiet system without much sacrifice for performance or a totally silent system at stock speeds.
