Choose the X2 processor if you want to do multi-tasking, like running a lot of programs at the same time. The "normal" AMD processors are more for gaming, and if you want to spend a lot of money. I'd go for a AMD FX55 or FX57.
about the AGP/PCI-E, PCI-E is the future, and not many AGP graphics cards are being built as we speak.
For graphics card choice i dont know what the main thing is you want to do with your computer, if your going to do some hardcore gaming, i'd suggest a 7800 or a X1800. For playing LFS a 6800 or x800 is enough to keep it running smoothly.