You can do this. But I doubt that it will make any real audible difference. Just about the only way it could help would be if you needed every bit of power the RX-V2700 can put out into two channels alone, which is extremely unlikely.
I recommend that you hang onto your old receiver until you are certain that everything works on your newer receiver. Then, if you don't want a second system, say, in your bedroom, I would advise you to either sell it or give it to a friend. I recently replaced my old RX-V730 with an RX-V2700, and I am giving away my old receiver to my mother, so she will have an upgrade. Basically, old surround receivers lose most of their value quickly, so you will not get terribly much from selling your old unit (though more than I would get for my old RX-V730).
