I think your AVR would be fine. It is 170 watts per channel into 8 ohms, or 270 watts into 4 ohms WHEN ONLY 2 SPEAKERS ARE DRIVEN. Or it is 120 watts per channel when all 7 speakers are driven. This is still a good size shared power supply. You are never going to use all power for all speakers concurrently.
The 804 is considered an 8 ohm speaker, but the impedance will drop down to 3 ohms (not entire sure where). I think you may start having challenges with an amplifier that is 100 watts or less, but it still would work. With your specific AVR, I think you are fine. If you really wanted to, you could always attach an external amplifier using the Left/Right Pre Outs.