ntune sucks, forget about it
for ocing within windows use clockgen, send me a pm with your email address and ill send you the clockgen beta. it was removed from the author cause its buggy, but its better than nothing.

took me 5 hours googling to find that beta finally on some ocers ftp ^^

how are you testing stability?
did you increase chipset voltage to make sure the chipset isnt holding you back?
check the manual or teamgroups site for what settings they recommend, ddr2 1300 is really pushing the limits...

your cas4 results are very nice!
im pretty sure its faster than 1300 555... go and try it out
and maybe your mem is good with cas3 as well so maybe cas3 with cmd 1t would be even faster

and its a LOT less problematic to run sub 1ghz memspeeds on 680!

yeah there is a teamgroup rep here on xs but they are usually very busy.
i just hit him up on msn and told him about this and he said hes going to look for the thread. maybe hes only checking the tg support section so maybe post a new thread there and link to this thread here.

about losing the warranty... seeing as the memory didnt come with the heatspreaders they were advertised with and that they just fell off i dont think they will refuse your rma. the memory was not in perfect shape before you got it... having said that, dont bench any further with 2.5v for now.

a thing i learned the hard way: always try your new hardare at stock, ALWAYS! and then mod it or void the warranty by ocing and overvolting and voltmodding it.