Thanks for all your incite, guys. Very much appreciated on this end.
Just to re-affirm, I have infact done my homework on all this and yes: the cards I was researching were AGP and not PCI/E. I think what I'm going to do is go ahead and bump up to 1.5 or 2 gigs, get the P4 EE 3.4 processor (I know it's not a that big a leap from what I have, but they're only $49.99 for Christ's sake!)
and then go with the Geforce 7900GS. I should see at least some sort of improvement from doing all of that! I'm playing a few other games that go beyond the hardware reqs. of AH. Stuff like Crysis, Oblivion, Star Trek Legacy, ETC. If I was just playing AH, I wouldn't even bother with the video card, but my current card struggles a bit while playing Crysis ( I have to put everything at or near the bottom for detail levels and effects).
I hear they're thinking about making the Geforce 8600GT/GTS for AGP.
I don't think AGP has the bandwidth to support detail levels akin to DX10, so what's the point? Oh well.. Again, thanks for all the suggestions and such.