An SSE variant is best if supported by the CPU. X2 has support inclusive of SSE3 so no worries. However, in the past different versions have been specified so I don't know if SSE, SSE2 and SSE3 support is now generally included in the "SSE" compile or if those available in your link literally only support the original SSE.
It's all academic anyway with a peppy CPU and undemanding videos but maybe SSE would help with some higher resolution XviD or h.264 (if ffdshow's decoder is utilized in lieu of a hardware accelerated alternative).
For conversion do the google dance else go directly to videohelp or doom9.