marantz 6400 or better??

i have a week to return the marantz 6400. i honestly dont know much about amps and such. now i got an av receiver to perhaps have ht soon. but i am driving a pair of dynuadio 52 and the amp is almost to its max and the speakers are still really low. now, the receiver rates at 6 to 8 ohms max load. the dynaudios are 4ohm loads. WHAT does this all mean.

thanks for uncunfusing me.

so, is the marantz 6400 a good selection for me. my number one is music anbd then movies, but mostly for movies just so that the music scores sound good.