SuperPi especially. For 32M you need speed (bandwidth), for 1M you need timings (latency). Wprime\PiFast im not sure how RAM dependent those are.
I dropped my multi on my RAM to 2:6 and my timings to 6-7-7-20, and noticed a boost in 1M, but my 32M was doing a lot worse. .
All GTX 280's support software voltage tuning. There is also a EVT patch to allow more than it normally allows.