I'm a bit clueless when it comes to computer hardware, so I figured you guys would be the best to ask.
I bought my computer in late 2010, and has
-a LOGISYS PS480D 480W ATX12V power supply
-a Radeon HD 5450
-AMD Athlon II X4 640 3.0GHz Processor
-4GB DDR3 system memory
not sure what else to add but it's pretty much this: http://www.walmart.com/ip/GUA103SE/15231528
The 5450 is pretty weak, especially when it comes to the games I like (Skyrim; Anno 2070/1404; Starcraft II; hell, even fullscreen Minecraft gets a bit choppy). I'm a bit shallow so I'd prefer playing them with max settings. Now that I have the money for it I'm considering upgrading to something preferably under $400 (like an HD 7870). The problem is, I'm not sure if graphics cards at that level would require a new PSU that would better suit it, when it comes to things like wattage or connectors or whatnot.
Is an HD 7870 good enough, and would I need a new PSU for it? Any better graphics cards in that price range? Specific recommendations would be nice. Thanks!
The PSU in your PC is a poor quality unit. It isn't really a true 480W PSU. Graphic cards get all their power from the +12V rail of the PSUs, and yours is rated at only 16A for a total of 300W available on the +12V rail. What all this means is that the HD 7870 may be a bit much for the PSU. At max usage, the card will require about 13.4A from the +12V rail. I would suggest a lesser card or replacing your PSU with a larger, better unit if you want to use the HD 7870.
What resolution is your display? That is the main determining factor as to what card you will need.
For some reason, I assumed you were using a lower resolution monitor. Maybe because of having the HD 5450. But at 1080p, you will need at least an HD 6870 or GTX 560 class card for max settings. So maybe the HD 7870 isn't so overkill after all. But the Athlon II x4 640 will bottle neck it some. But it will still provide you with fast frame rates at 1080p and max settings.
Do those seem alright? Any other factors I need to consider before buying to make sure everything is compatible and fits with my system (sizes of the parts, additional wiring, etc.)? Sorry if I seem a bit paranoid but I've faced numerous computer issues from rash decisions before, and sure as hell don't want to mess up this time around.
While the 80 Plus Gold PSU is more efficient (naturally) than the Bronze, I see nothing wrong with the 520W PSU. And your card selection is fine too. Btw, I have that same card (but in the HD 6950 variation) in a new build I just finished. I was afraid the 2 fans would be noisy, but not so. Nice and quiet. At idle, anyway. Just be sure you have the room for it in your case. I believe it is about 10 1/4" long.
Do you know the make/model no. of your motherboard?
And btw, since you said the 7870 might be a bit much because my processor would limit its performance, would something slightly weaker be a better fit at this point? Or should I just go with it and maybe upgrade the processor in the future?
If you have any thought of upgrading your processor in the future, I would stay with the card you chose. Your board can take almost any Phenom II X4, so you have a wide choice of more powerful CPUs. But the K10 line of CPUs are not made anymore and are getting scarce to find. You may want to think about a CPU upgrade before they are all gone... or demand high prices due to scarcity. Newegg still has the PHII X4 965BE at a reasonable price: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
If fact, if you hurry, you can save $10. And every so often you can find a 955, 975, 980 on ebay.
If you decide to stick with the Athlon II X2 for awhile longer, I'd still get the HD 7870 because you game at 1080p and need all the graphic processing power you can get. Even at the risk of CPU bottle neck. If you don't plan on ever upgrading the CPU, You might back off to something like the HD 6850 or GTX 460, but nothing less.