Currently I am using my Yamaha 2400 as a preamp, running it though an Adcom 7605 five channel amp and two Outlaw m-200 mono amps. At this time I do not need a preamp, however when I move my system to a dedicated room I want to keep the Yammie in the family room. At that point I will need to purchase a preamp.
I have also been told that while using a receiver as a preamp can improve overall system performance, buying a real preamp such a the Outlaw 950, Adcom GTP 880 or Rotel RSP 1068, will really make your system sing.