I couldn't follow the whole discussion, pardon me if this has already been discussed.
RTI a7 are amazing speakers, your AVR seems to be the weakest link for listener with 80% orientation towards music.
I don't know your budget also, but according to the discussion from PMs you've sent...
I'd suggest you to go with Marantz 7025 2 Ch power amp. Those speakers need good power to perform adequately (I owned RTI a5 earlier and I was amazed at the SQ when driven by sufficient stereo amp) so since you have a Swiss knife of digital audio ( read Yamaha Wxc50) a power amp ( any brand should do, I'm just suggesting Marantz coz it pairs well with Polk RTI) with wattage rating above 100 wpc is what you should be looking at. Power amp will give you a flexibility to accommodate easily when you upgrade to an AVR with preouts.
Alternatively you could look at good analog integrated amps with similar power rating. Go for pre-owned amps if the new one don't fit the budget. Listen at FMs place or audition rooms before taking a call.