My other components are 2x1GB ram, a 7200RPM hard drive, two DVD-RW drives, an Intel DP965LT mobo, and a Core 2 Duo E6400. I'm thinking I'll get around 650W or higher in case I upgrade in the future. My main question is about PSU fans. My current PSU has the fan on the back, but I've noticed a lot of them have fans on the top, and my case doesn't have an opening above where the power supply goes. Do I have to get another PSU with a back fan? Or are the top fans intake fans? What about PSUs with bottom fans?
Finally, what's a good PSU that works with my case?
PSU's don't have "top fans". The picture you see of the PSU's with 120mm fans are shown with the psu turned over. The fan is on the BOTTOM of the psu and it DRAWS air into, through, and out the psu's back grill. Also, the psu mounting holes on your case will only allow you to mount the psu with the fan in the "bottom position" anyways, so you can't mess it up. Understand now?
Is that a good power supply or should I stick with one of the others?
Avoid the Xigmatek.
Another good PSU would be the Thermaltake Toughpower 750wt. Having used both the PC P&C and the TT Toughpower, I can say that the Toughpower is a lot quieter. For reviews on good (and bad) PSUs, go to http://www.jonnyguru.com/index.php . Also, I doubt need a 750wt PSU. Use a PSU calculator such as:
That shows the actual power consumption of each kind of GPU setup, add your CPU TDP and 10-15W per HDD or ODD, 20-30W for the motherboard and you have a good estimation of power usage. Ideally, your system should run 50-70% load (of the PSU) with all components fully loaded (for efficiency purposes). Power supplies acheive maximum efficiency between 40-55% rated load.