Yah I don't know if it'd really help. I heard that the 128mb cards were gonna have SDR, which would definitely be useless, but appearantly these have DDR?
Look at say a 32mb GF2 GTS, then a 64mb one. When they came out, there was a very small difference in performance. I'm not sure if that has changed much, because most benchmarks now are the 64mb I assume.