OC QX6700 - SUPERTALENT on E-VGA 680i

Helo,new here...
NO EXPERiENCE in overcklocking and need help please...
After paying a lot, i bought myself :

qx6700
8800gtx
2gb supertalent (T800UX2GC4 - 2GB kit, 800MHz, PC6400, 4-4-3-8 latency)
e-vga 680
zalman 600w psu
zalman 9700 cooler

Changing the multiplier i have reached approx. 3,7 stable....BUT the
core temp on full load reached till 75-80 degrees...
1) I'm thinkink about Tuniq tower cooler ...is it worth it ?
2) If i o/c with fsb and not multiplier (ram unlinked) has difference ???
3) Leaving the ram timing at auto i pushed the ram at 1066...i saw no performance gain.
When i underclocked the ram at 728 i managed timining 3-3-3-5 1T
(Ram voltage 2.1). How much more voltage do i increase to have the same timings (or about) at 800??? Can it handle it ???

thanx

[b][/b]