The i7 860 is like 15-20% better then the QX6850 regardless of clock speed.
Both 775 and 1156 Sockets are dead ends for upgrading the CPU the 1366 has the option to go to a Six-Core i7 in march next year but really I think Intel will release another sockets that will have SATA port with RAID from the CPU with integrated duel 16x PCI-e 2.0 support and maybe tri-channel RAM again by Q4 of 2010.
So I go for the i7 with 4GB 1600Mhz of ram and boards I suggest you look at are:
GIGABYTE GA-P55-UD4/P , GA-P55A-UD4/P (with or without P)
ASUS P7P55D PRO, P7P55D-E Pro