They must have revamped their tools pretty heavily - I found them wicked buggy last time I used them, although it's been a while.
I like afterburner
Super easy interface, excellent monitoring.
Drol, reading over on Xtremesystems
a lot of the guys there seem to think going for max stable memory clock first, then working the core clock is the best way to go.
As far as the 260 goes, if you got a good overclocker then I'd bet you can see some gains, just take it slow, no more than 10-20mhz at a time, then test for artifacts and stability.
As far as your shader and core clocks, they are linked on mine, I can't change one and not the other, but I'm not sure about yours. If yours are unlinkable, I've heard a high shader clock will net you more fps than core - don't know for sure.
Looking forward to your results though.