Well....I think it depends on the components. Here is how my progression went:
Marantz 4300
HK 525
HK 525 with an ATI 1505 amp
Sherwood/Newcastle P-965 pre/pro with ATI 1502 and 1505 amps
I would say the biggest difference was going from the 4300 to 525, and after that, it was adding the amp.
-curtis