The RC-64 is a very efficient(99dB) speaker. The Onkyo TX-SR805 has very high quality amps and power source usually only found on receivers
at a much higher price point. On this and other forums many members with similar setups have chimed in and touted the capabilities of the 805.
Get the RC-64, take it home, hook it up and listen. If not satisfied, buy an external amp to power the 64 or take it back and get the 62. Keep in mind,
you might get the "bug" and may want to upgrade to the RF-63's or 83's, then you would already have the RC-64.
Bill