Suggestions/opinions on computer parts

It's high time I get myself a new computer. A friend of mine compiled an initial suggestion list of parts to get, but he's selected some high grade stuff that I'm now trying to compromise on in order to get the total price a bit lower. I already switched the HDD and such and now pondering on graphics cards.

My friend selected an "Asus Radeon HD 3870" for PCI-E with 512MB 256-bit DDR4.

The damn thing costs quite a bit (at least here), so how much better is it compared to, say, the much cheaper "Sapphire Radeon HD 3650" for PCI-E with 512MB GDDR3?

Or rather, is the 3650 one that much inferior that I shouldn't get it if I'm not quite that concerned with getting an über powerful card? I mean I do plan on playing PC games, but I don't need top of the line performance if it'll cost me an extra few hundred euros. Do the DDR4 and GDDR3 make a big difference?



EDIT:

Also, cases. My friend selected an Antec P182 Gun Metal Black with an Antec EA 650-EC EarthWatts 650W ATX powersource. The P182 case is really nice and the compartment system for the powersource and harddrives is pretty good, I'm told. But is it all that much more quiet, less straining on the components, effective, useful and all that compared to something simpler like Codegen's M-610 ATX case with an 400W powersource? I play with headphones, so running noise is not that big an issue, I just want the case not to strain the components with heat.

How likely am I to actually need 650W or is 400W usually sufficient?

Jam it back in, in the dark.

If you have multiple fans in your system, multiple hard drives, a powerful graphics card, etc, you should go with 650W. You probably don't so 400W should be sufficient.

Antec makes really awesome cases but they're also freaking expensive. Look at product pictures (Newegg should have them), consider your existing internal components and any plans for future expansion, and go with whatever best suits your purposes. I have a cheapo Cooler Master and I prefer it over my old Antec Sonata.

There's nowhere I can't reach.

3650 is okay. It's not inferior. It'll run games, just at a lower resolution. Take a look: ATI Radeon HD Refresh: The 3650 and 3450 Arrive - HotHardware

The nVidia 8600GT will give you better performance, but it's 20 dollars more. I don't know if the price/performance difference matters to you. I do want to mention that sales on 8600 seem quite popular and it usually approaches the same price as the 3650

DDR4 and GDDR3 won't make that much of a difference.

Calculate power usage: eXtreme Power Supply Calculator Lite v2.5

This thing is sticky, and I don't like it. I don't appreciate it.

I am pro-ATi, but it's clear that Nvidia is the best bang for the buck these days.

I'll be getting an 8800 GT myself, in the near future.

I am a dolphin, do you want me on your body?

That calculator is pretty neat, thanks xiao. 400W should be fine for my needs.

As for the cards, Nvidia's sets manage to confuse me worse than ATi's. There's a dozen manufacturers for apparently the same model, but the price differences are huge. Is Asus considered a cheapo card maker that shouldn't be bought (concerning the 8600GT 512M for instance?)

I was speaking idiomatically.

nVidia actually doesn't actually make the cards. They only provide the blueprint for other companies to manufacture the cards. This means anyone can make them, as long as they meet nVidia's basic requirements and pay them some licensing. In fact, many companies overclock their cards or slap on extra memory to stand out from the competition. Good companies for nVidia are BFG, XFX, EVGA, Gigabyte, MSI, and ASUS. If you're unsure, put their name in google and see what people say about them.

Asus is a safe bet though. They're huge in the OEM/ODM business, which means you can sort things out with warranties and failures.

Just make sure your retailer has a good RMA policy, aka not Tigerdirect.

What kind of toxic man-thing is happening now?