Problems with Pc game

I'm currently trying to play the expansion packs for Gal Civ II, the Dread Lords which is the original plays perfectly fine, but the expansion packs which according to stardock doesnt require anymore than the DL, don't play properly and when I get into the game it lags hard until I zoom out, I've tried taking the graphics to poor(lowest setting) and playing on a smaller map, but it didn't make a difference.

Heres what the games supposedly requires according to the expacs manual.

System Requirements
To play Galactic Civilizations II you will need at least:
1000 MHz Pentium III or AMD equivalent processor 256 MB of total system memory A 32 MB video card with hardware T&L (nVidia GeForce 2 or ATI Radeon 7500 or better) DirectX 9.0c compatible video card CD-ROM drive (if running the retail version) 2 GB of free hard disk space
We recommend that you have:
2.2 GHz Intel Pentium 4 or AMD equivalent processor 512 MB of total system memory 128 MB video card with DirectX 9.0c support (most modern video cards that are not integrated into the system board) 2 GB of free hard disk space
Windows 98, ME, 2000, XP, or Windows Vista are necessary to run this game.
Installing

What I have is:

Pent 4 1.8ghz
2gigs of DDR ram
256mb ATI Radeon 9250
120gig hardrive

Now on the stardock forums I was trying to get help, and one guy said it was that my video card only support dx8.1, but I don't think thats the problem seeing as how I have about 10 other games that say they need direct x 9.0c supported video cards and they play fine on my pc.

I'd appreciate any ideas, and help.