Actually, 8K7A does not support SSE yet.  Palomino works fine, but SSE is still disabled.  The only AMD761 based board that that supports SSE I am personally aware of is the K7 Master (I had one before with a Palo).  I've heard Gigabyte's 7DXR have it enabled, but I have not tried it so I cannot personally confirm this.
Tako_chu