My guess is that it won't make a bit of difference. I note that the two channel power rating of both receivers is the same, so I am sure the power supply is the same. If you are running a 5.1 system, I would bet it is the same 80 wpc x 5 for both receivers, as the same amount of power is being split five ways with either one.
it would be great if the 6.1 running at 70rms would change to 80 rms when using a 5.1 on the T753 in this case the T753 would be a better choice. to add another speaker generally increases the sound than the increase in watts, would this be correct. Hawk could u give me your opinion on which one u would go for. while im at it would it be ok for me to get q8s KEFs for the front and back with a good sub, since the speakers are 120watts like the Q1s. thanks