Sorry, OP... one more point. When I was researching like you are now, the experts here recommended the XPA-3 for only the fronts and center, driving the surrounds and rear surrounds with the AVR. I believe they already knew what I know now, that both the amp and Grand Towers are overkill and not necessary for the surrounds. When I went to the Emotiva site to buy the XPA-3, they had none in stock and no expected availability. I prefer to buy from the mfg simply for ease of support and warranty, so I bought the XPA-5. Then of course had to get 2 more Grand Towers.
The truth is, I really don't think I'm getting a noticeable difference from the surrounds with the amp and Grand Towers. I could have bought smaller speakers and the XPA-3 and likely not notice any difference.
BUT, I have now forgotten the price, love my system and won't change it in the near future. Good luck!