Alright, here's the 4gig ram, for just below $40:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148262&cm_sp=Cat_Memory-_-Featured_Brand-_-20-148-262And here's a 6gig on for $65:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820161451Both of these are good and should run anything, but the 6gig is clocked higher (and, naturally, is more) so it would ensure your computer stays current for a bit longer, perhaps even a year or two of hitting max settings on everything.
Shop around a bit, though, clock setting won't make too much difference so in general any DDR3 you find cheaper and/or higher capacity should be good. Check reviews to make sure it isn't dying on people, though (it usually doesn't)
I can't find the specific CPU I recommended on the site that I use, so you should look around for it a bit (AMD Athlon II X4 920), but here's a similarly priced one that's still faster than mine:
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103885I don't know much about intel processors, but the top-model ones go
much higher than AMDs (although you don't really need that sort of speed for gaming, it's generally for video editing). I also hear AMD works better with Windows (and that Intel is built for macs) but that's just hearsay.
You should get other people to weigh in on the merits of Intel vs AMD.
Any of these cards should do whatever you want them to:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130572 1gig DDR5 (vidya cards go higher than RAM in terms of RAM clock, RAM tops out at DDR3 while vRAM goes to DDR5)
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127521 1gig DDR5, seems identical to previous.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127573 This is a GTX, while the others were in the GTS series, so this will yield better performance. Enough to warrant the $30 extra, I'd say.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814133386 Here's a much cheaper one, with 1gig DDR3. This should be fine, but don't count on it running things at max for very long, maybe a year or two.
EDIT: Huh, I suppose I was just terrible at shopping when I went after a motherboard last time.
Here's one that looks good, and has everything you need to use the parts I recommend above:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157195If you decide to go with this one, check for some specifics when you shop for other components:
RAM should be DDR3, 1600 or 1333 (lower won't save you much so you may as well spring for these).
Check the CPU to make sure it takes the AM3 slot.
And check that any graphics card you're after will take PCIe 2.0 x16. (really, just check for the 2.0, you won't find a good card that doesn't take some sort of PCIe x16)
This board will take all the RAM you'll ever want to throw at it.
finally, you'll want a PSU:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371031620 watts should be enough, and its power pin matches the one for the motherboard I linked.
You should probably print out this list and have the computer shop check it out, though, because I'm admittedly fairly new at this. However, if they tell you that this system is way underpowered and that you need some fancy $1000 rig, keep in mind that they're probably just trying to sell you the most expensive thing they have for commission.
Pricing:
Cheapest of the items in this post:
4 gig DDR3 RAM
3.1 ghz quad core
1 gig DDR5 vRAM GTS 450
Motherboard
620 watt PSU
$413 (I'd go with this just for the totes rad pricing)
Most expensive:
6 gig DDR3 RAM
3.1 ghz quad core
1 gig DDR5 vRAM GTX 550 (yes this is actually faster)
Motherboard
620 watt PSU
$467 (Not too much more, but would the performance boost be worth the extra 50~ dollars?)