I currently have a 7600 GS agp card in my system which has an Opteron 180(2.4 ghz) chip(its a dual core chip, but only can only run single core with the mobo I have) and 1g of memory. This is basically my dvr machine and its fine for that purpose, but trying to actually watch TV on it is no good. On a digital channel, the sound will eventually go out, and the FPS really slows down. On analog channels, the sound remains but FPS goes down some.
I'm hoping I can just put a new card in and the cpu is fine. Opinions there? and what card do you recommend if its just my card that needs updating. Don't suggest any cards that would take up more than one slot, I don't have the room.

Well, the 3850 agp card is about the best, and most expensive agp style graphics you can get...Though I'm not sure you'll get the most out of it with your system.

Currently they range from $114 after rebate, to $199.

Gaming power isn't really needed for a DVR so the 3850 would be overkill; I believe even the Radeon HD 3450 has the same video decoding abilities as the 3850.

Nvidia's pretty much abandoned the AGP market, so you'd probably have to go with an AMD/ATi product if you wanted a reasonably new graphics card. While newegg does show an Asus Radeon HD 3450, the comments seem to show people having some driver trouble with the card. I'd suggest you choose between the two 3650s (Sapphire's card or HIS Hightech's card). They have the full Avivo HD video decoding abilities plus can do a bit of lower resolution gaming should you want to play a game or two on your TV (recently I had some fun replaying KotOR I and II on my TV using my DVR). If you can use HDMI go with the HIS card since it comes with a DVI to HDMI connector, but if you're using component go with the Sapphire card.

Honestly DVR activities rely very little on GPU power, I can pretty much guarantee that your 7600 is maxing out the AGP buss (Which is why Nvidia quit making agp cards, there is no tangible benefit). You already have a solid cpu so I doubt the wall you are running into is cpu related. However since I used to use my machine as a media center/dvr Alot before I switched to using a ps3, I can tell you one thing. One gb of Ram is not enough, that gets eaten up quick. Chances are all your problems come from your streaming and transcoding being forced into the swap file of the hard drive and that will slow down a machine badly.

Just to clarify, I'm not streaming it to my TV, I just meant I'm watching TV on my computer via the TV card and gbpvr.

I was aware, was just covering all the bases.