The only version of OSx that i have been able to have full support on my Toshiba x205sli6 is Leo4all 10.5.2 v3.
But I have a different graphical accelerator than you do.

---

REAL Mac Pro - OC 3.1Ghz -2x 2.8GHz -XFX 5770 1GB / 8800GT- 10GB RAM -1.55TB - 2 SATA Optical - Lion / Snow Leo / Windows 7 x64 / in AHCI Mode
Toshiba X205-SLI6 17" Dual 8600M GT 256MB SLI, 400GB -
Win7 x64 / Lion vanilla / Snow Leo Vanilla - Full QE/CI - WiFi Dell 1390 (pin 20 removed) - ALC268 VoodooHDA - working fingerprint reader, Bluetooth well everything but display brightness changing.
Dell poweredge T110 2.8ghz 8 core xeon server 8gb ram