Pick which ever one fits your budget and desires best. There really isn't much difference between any of the main players in the better AVR's, Onkyo, Yamaha, Pioneer, Denon. They all have really good Power supplies and amps. The Denons might be a little better with their P/S's and amp sections, but most people will never need the ability to play a speaker array at just over 1 ohm of resistance as some of us on the board have done not too long ago
If the 605 has all the bells and whistles you want then buy it. If the 705 has one particular feature you like better and can afford the price increase then buy that one. And if there is a difference in sound between receivers, tone controls can be used to adjust the sound to your taste.
