Video card for AGP

[Obiwanshinobi]

Feel free to move it to the Hardware section if you see fit to do so. I just thought people who are not into arcade sticks, PCBs and stuff may be in touch with the PC hardware market nonetheless.
I'm gonna get myself a new video card for my old PC (AGP, Athlon 2000+, 1 GB RAM, WinXP). Yes, AGP, not PCI-E. Used to have a GeForce 6800 XT 128 MB, but I'm currently using a replacement Radeon 8500.
So, is there any particular AGP card I should be after? I'd like it to have at least 512 MB RAM, hardware video decoding and Shader Model 3.0 support fast enough to be of any use (it was more of a snake oil feature in 6800). I don't care much for SM 4.1 and DX 10.1 since my CPU is so old anyways.
I'm particulary interested in two models fetching similar prices:
Radeon Gigabyte HD 4650 1GB DDR2 and 3850HD 512 MB DDR3.
Do you think the latter's faster memory would give it any perceptible advantage over the former in case of, say, loading huge bitmaps into the video RAM? Or just about any advantage? Furthermore, a few years ago there was some talk about baking anti-piracy measures in the PC hardware. Did that happen eventually? If any of those Radeons comes with a stinking surprise of the sort, I'd rather re-buy a 6800 and put up with the lack of hardware video acceleration and crappy SM 3.0 support (effectively lack of thereof).
Which AGP video card model you'd buy for such an old machine?
P.S. According to internet people 3850 is faster but 4650 uses half as much power. Of dear. Since the highest resolution my CRT can muster is 1280x1024 at 60 Hz, I wonder is there ANY game out there that won't be bottlenecked by the CPU to the point where 3850's speed advantage hardly matters. In 1280x1024 on 17'' I won't see much difference between AAx4 and x8 after all, whereas the power consumption will make quite a difference of another kind.

[ED-057]

Considering that it's going into an older system you probably want to pick whichever card meets your requirements that is the cheapest. Was the GeForce 6800 fast enough or do you want something better? The 6800 had a 256bit memory bus so the Radeon 4650 with 128-bit DDR2 probably isn't going to beat it in many applications. The 3850 should definitely be faster. Perhaps a Radeon 4670 would be a good choice, or since you don't need DX10, a GeForce 7900GT.

Here is a handy page to look up video card specs (although it does have some errors and omisions):
http://www.neeyik.info/3dspecs/

[Obiwanshinobi]

Not sure if my 6800 was really 256-bit as XT's 128-bit iteration also existed. It was okay, speed-wise, but would choke on any shader above 2.0. Also, H-L2 Episode 2 and Need for Speed: Most Wanted didn't run all that well on it (with all details maxed out, that is).
I'm leaning towards that 4650, although 1 GB DDR2 sounds like snake oil again. The thing is, I like the idea of lesser power consumption and am in no hurry to buy a new PSU (500W here, but not exactly upper shelf). Alas, it apperas to have issues with certain motherboards, but that's a gamble I can't escape.

[Jockel]

Go with the faster card. It's not like you're gonna max out that whole gigabyte on that computer.
Also consider getting a whole new mainboard and CPU with it, since pcie cards tend to be cheaper. Besides that, your system will probably feel too slow in a year again, so a full upgrade is pretty much inevitable. Buying an extra card for a system that's gonna be obsolete soon seems like a waste of money for me.