You buy a PSU from a reputable company for several reasons.:
- Should the PSU fail, a good reliable PSU from a reputable company will not kill your entire system when it dies.
- No PSU puts out what it's advertised when it heats up. When the PSU warms up the power output lessens, it's a known fact. Therefore, a good reliable PSU from a reputable company will ensure that the loss of power output is minimal.
- There are several other reasons why you would want to get a reliable PSU from a reputable company but they are very techincal and take a long time to type and I don't have a long time to type. All that you need to know is this is where I would get into capacitor quality (which, if you were to touch with your bare hands you would die) and overvoltage protection.
PC Power and Cooling, Enermax, OCZ, Antec, and Zippy are good PSU's.
When looking for a good PSU you want one with a lot of amps on each rail, especially the 12v rail. I've seen each of these companies sell a 500w+ PSU with very little 12v amps for the same price as another one of their PSU's with a lot of 12v amps (35-40 is a good number). Why this is, I don't know.
You want to avoid dual rail PSU's. Supposedly they're supposed to work as good or better than single rail PSU's but when overclocking your best bet is a single rail PSU.
So now that you know you want a single rail PSU and now that you know you need a lot of amps on each rail and you know what companies you can trust, you can purchase a PSU. I don't like to recommend PSU's because they are the heart of the system and I would hate to recommend a bad heart (although, I seriously doubt I would).
If you want me to recommend some single rail PSU's. I'd recommend:
Antec 550W Power Supply, 24-Pin, Model "TRUE550 EPS12V" - Retail
Output:+3.3V@32A;+5V@40A;-5V@0.5A;+12V@36A;-12V@1A;+5VSB@2A
OCZ PowerStream 520W Power Supply With Adjustable Power Rails With LED Indicators, SATA Connector, Model "OCZ520ADJ" -RETAIL
Output: +3.3V@28A, +5V@40A, +12V@33A, -5V@0.5A, -12V@0.5A, +5VSB@2.0A
ZIPPY/EMACS 700W Power Supply With SATA Connector, Model "PSL-6701P-SATA" -RETAIL
Output: +3.3V@30A, +5V@35A, +12V@45A, -5V@0.8A, -12V@1A, +5VSB@2A
ENERMAX 550W Power supply for AMD K7 & Pentium4. 24-Pin with 20-Pin adapters ( EPS 12V To ATX 12V and EPS 12V To AMD ATX GS), Model "EG651P-VE(24P)"
Output: +3.3V@36A; +5V@36A; -5V@1A; +12V@36A; -12V@1A; +5VSB@2.2A
PC POWER AND COOLING TURBO-COOL MODEL 510 ATX/ATX12V, 510 ATX+6, 510 Express, 510 SLI
+5V @ 40A, +12V @ 34A/38A, -5V @ 0.3A, -12V @ 2A, +3.3V @ 30A, +5VSB @ 3A, power=510W, pk. power=650W
If you can't help but go dual 12v rails:
ZIPPY/EMACS 600W Power Supply With SATA Connector, Model "PSM-6600P-SATA" -RETAIL
Output: +3.3V@30A, +5V@30A, +12V1@26A, +12V2@20A, -5V@0.8A, -12V@0.8A, +5VSB@2A (max total 12v amps = 40A)
Again, I'd do your own research before picking any of these. Picking the right PSU is a crucial step in building a computer. But anyone of these should fit your needs. You always want the highest possible wattage with the highest possible amperage. If you get a 465w PSU with 33a on the 12v rail. That might take a lot of devices but you may run out of power to power the whole system. Therefore, my recommendation is that 700w zippy with 45a on the 12v rail but it's expensive.