I'd say it depends on what you'd like to improve or where you find your current system lacking. Do you have a sub already? If not I'd say go for the EP. However if you've got good bottom end already and find you're running out of headroom then go for more power. However getting a sub may also clean things up as the M100's won't have to play the low end which is offloaded to the sub and the amp won't have to power those frequencies giving it a tad more room to operate as well. I think the EP unless you already have a sub. Anyway that's my 2 cents without knowing your specific details. Smarter minds than mine will be along soon I'd guess to give better perspective :-)

Cheers,

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1