Graphical Interface does not start

Hi! I'm having this problem in my home desktop. I have installed these new MoBo, CPU and Graphics Card -MoBo: ASUS P5B -CPU: Intel Core 2 CPU 6420 @ 2,13 GHz -GPU: ATI Radeon X550XTX while keeping to my old hard drive ST380011A. Before, I had a Pentium4 and I had installed debian with a realtime kernel but not 64studio, although I had in the past the 32bit version of 64Studio and worked fine. Well, I have formatted the partition dedicated to the OS (I have another mounted in /home) and installed the 64studio 2.0. Now, the GUI doesn't start. lspci reports "unknown device" for the graphics card. I should have checked the Linux support for it but I didn't. I've followed the tutorial but my /etc/X11/xorg.conf reads Driver "vesa" and still there is no GUI. I'm running the Knoppix Live CD with KDE now. I will try copying the "Section Device" lines of the xorg.conf I have in Knoppix to 64studio. I'll tell you if it works out or not. If I don't success, maybe I'll get another graphics card. Recommendation is welcomed. My budget is from 30 to 60 Euros for one with 3d acceleration just to play some simple 3D Game. Thank you Pablo