You can have 4 sticks of ram in dual channel, its just not as efficent, as you have to use 2 memory controllers. (1 on the first set of dual channel ram, and the other on the other set of ram)
Quick round-up:
-FX-55
-X900/7800 - wait until both are out, if you really don't care about money, then if they still go with the crossfire/SLI than get two of them
-DFI lanparty board SLI-D/SLI-DR
-1gb of G-skill ram LA's
-2X 10000 rpm WD raptors (If you want, Seagate 15k cheetah's with a good SCSI card)
-2X 400gb Seagate SATA HDD (If you need more space, I think I remember seeing the SLI-DR mobo has 8X sata ports
-NEC DVD burner
-NEC cd burner (if you want it, get one that can read DVD's as well)
-DD custom water cooling set-up
-Antec/OCZ/Enermax/Thermaltake PSU
-Big case, with plenty of fans, preferable 120mm one.