Upgrade to PCI graphics card from onboard video

First off, I would like to say that my Dell has worked well for me for the past 5/6 years. Now that I have started to play WOW (never got into PC games before) and my wife has started to play other games like Peggle and Bejewled, I can see that an upgrade is going to be needed from the onboard graphics. I have decided to build a new i7 for me and my WOW addiction http://www.tomshardware.com/forum/273256-31-build and pass this Dell down to be her computer (I know, I am greedy). I would like to know what the best PCI graphics card would be for this setup. I do not want to spend $100 on a PCI graphics card for this old Dell but I do want something better than the onboard graphics. This Dell does not have PCI express, only PCI slots. The MOBO has a spot for an AGP socket (I guess the socket cost too much for Dell to solder one in) and the BIOS has an AGP option, Is it worth trying to solder in an AGP socket? Is full details on WOW at decent frame rates too much to expect from the PCI buss?

In a nutshell, I am looking for the best PCI (not Express) video card bang for the buck (price/performance ratio) that will work in my old Dell and any other upgrade thoughts to buy me some more time before I need to build another PC. I would consider a replacement mobo that could use all of the old parts, but I hear that the Dell layout is not std ATX and other mobos won't fit. Any help would be appreciated.

System:
Dell Dimension 3000
Pentium 4 CPU 3.0GHz, 2.99GHz (Why it's listed twice, I don't know), 1.99 GB of Ram (Would like to OC, but Dell Bios is locked down)  
OS - XP Home Version 2002 Service pack 3
Hard drive - WDC WD800BB-75JHA0 IDE(Standard Disc Drives) 75GB for programs and OS (Currently with 23.4GB of free space)
WD External Hdd 1x 2500JB (250GB USB used for DVD video rip ) 1x6400AAV (640GB USB used for Music/iTunes/Pics)
Display adapter - Intel 82865G Graphics Controller
Monitor - Smasung SyncMaster 2343 bwx connected via stock Dell VGA cable (This box only has VGA out)

As a side note, under performance options I have the following selected:
Visual Effects - Adjust for best performance
Advanced - Processor Scheduling - Adjust for best performance of Programs
Advanced - Memory Usage - Adjust for best performance of programs
Advanced - Virtual memory - Total page file size for all drives 2038MB
Data Execution Prevention - Turn on DEP for essential Windows programs