I know the 630 can do a good job on the RTi10, not sure about the 12. I am using a 15 year old Adcom GFA-555 with my Denon 3805. It is only rated 200WPC into 8 ohms or 350 into 4 ohms, but is has no problem pushing my inefficient Veritas speakers. You should be able to get a used one at a very low price.