why did you buy a separate HT amp?

I think you just answered your own question, pardner.

Have you considered separate amps for only the front channels and let the AVR handle the surrounds? Since the surround channels rarely get driven hard, it would be a more economical solution. You could even get away with the AVR handling the center. With it driving only 3 channels it should be able to put out the volume you want. This will make your setup better for music too.

I'm with Pacific Island Audio. I use a separate 300wpc amp for my front speakers, along with a passive pre-amp with pass-through. Maximized two channel, not as much strain on my multi-channel amp. Enables bi-amping of center channel with the open channels on the surround amp.

Enjoy,

Dan