Pat, I've also read those claims about a separate amplifier helping with the "over all sound" of the speakers, but no factual basis for them has been shown. On the contrary, both basic audio theory and the results of properly controlled blind listening tests indicate that a correctly designed modern amplifier, regardless of whether it's in a receiver or separate, amplifies transparently, with flat frequency response and inaudibly low noise and distortion within its designed limits. Nothing more than this is possible; there are no miracles which occur when the amplifier is put into a separate box. Unless the present power of your 705 is inadequate for safe listening levels at your position(highly unlikely), buying still more maximum power capacity is money wasted. Unused power headroom is simply that: unused.
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Enjoy the music, not the equipment.