I know this is an old thread, but some people still might be trying to upgrade there inexpensive Optiplex GX-270. It is correct about not being able to add a more powerful power supply, so because of that you are limited to up grade choices for games. I still use the game Axis & Allies, and this game is about the max my old Optplex can handle, and it only handles this game OK. I did purchase a GeForce 6200 512MB low profile (capable) GPU for any chance to play this game correctly, the stock GeForce4 MX 64MB GPU just plain hung up and shuddered a lot . I added a 1Gig memory stick to the stock 512MB of memory my box came with, and this seemed to smooth out the game action a bit also. With all of that done, I can play Axis & Allies in a high resolution with only slight hesitation in the game play when there is a lot of heavy action for the graphics to keep up with. Also, one other thing that actually helped out a little was to turn off any thing running in the back ground that you do not absolutely need, simply go to RUN>TYPE IN MSCONFIG>GO TO START TAB and shut off every thing you can. This gives your CPU less junk to keep track of and frees up processing power.