New AGP card

Hay guys, in dire need of help here. I'm seriously out of date on information regarding gfx cards and I need a new one.
I've got an old system and want to boost it somewhat (don't have money for a new one...)
P4 3Ghz HT, 1GB DDR, Radeon 9800Pro right now.
I'm thinking of buying an X1950Pro, HD2600XT or 7950 GT. HD2600XT would be cheaper but I read performance isn't as good. But does it even matter on my system? Will I get any gain at all with these cards? Don't want to pay for nothing...

Them new S3's are pretty cool.

Don't worry - you won't be paying for nothing. Even if it doesn't work or make a difference to your system you can still take it out and just plug it into your TV so it improves its video and DVD performance.