The Athlon MPs were only intended for use in multi-processor systems. AMD is charging a premium for them. The desktop version of the Palominos (not MP certified) should arrive in a couple of months and they will debut at faster speeds. As everyone should know by now, the Palominos have SSE support. I'd say wait for the Desktop Palominos to arrive to get the SSE instruction set support.
I play a couple of RTS games (i.e., "Earth 2150", and "The Moon Project") in which the mutli-light source graphics effects are computed <b>only if</b> the processor has SSE capability. With SSE, the objects in the 3D world is brighter and more colorful in low lighting conditions (these game have changing day/night cycles as oppose to static unchanging broad daylight scenes). Without SSE, those same objects looks dark, cold, dull, and bland in low lighting conditions. Not saying this happens alot, but I rather have SSE supported.