Luis 32,
I had the same situation recently. I bought an ADCOM 7700 5 channel amp and continuted to use my Denon 3600 receiver as a pre-pro. (BTW, I became friends with some people at a local hi-fi store and felt it was important to support him this time) The was a difference in dynamic range and depth, however, there was no comparison to the difference it made to use the 950 pre-pro I got this week. I echo D'Arbignal's opinion on this, the pre-pro produces a greater difference than the amp. Good Luck!