Actually I used precompiled binaries from wuala.com. SSE4a is definitely faster than SSSE3/SSE4.1-4.2/AVX in 32bits and slightly faster than Core i7-optimized binaries in 64 bits. 64-bit miner is almost 2 times faster than 32-bit. My CPU is 2600K.
Correct! This is true because twobits, whose binaries you are using, compiled his own libraries for minerd specifically for the amd64 miner. You should expect a healthy boost in hash-rate when he gets around to updating said i7 miner.