Oi, thats a toughie. I would've recommended checking your speaker specs before buying an amp :P You could've gotten a better quality amp matched to your speakers for the same amount. However, for what you've got, the amp is gonna put out 500W at 8ohms no matter whats hooked up at the other end. Best thing to do would be turn your
amps down by 6dB or so. That should give you some breathing room. You have to bear in mind however, that your amp is gonna be running a little cool now, so don't judge anything by the LED's on the amp. Don't attempt to get it running at nominal, you'll just fry your inputs.
Hope I helped!