Preamp or Amp?


I started a thread that has gotten no responses so I've started another one. Hopefully this is much more direct. I have a simaudio intergrated amp. Would I hear a difference moving up from an i-3 to a higher i-5 or Classe' 151 OR would I be best to move my budget up slightly and begin the trek down the seperates road.

Does the Preamp effect the overall presentation of a system more then the amp? I will be using Polk Audio LSi15 speakers. At what level of separates will I hear a significant improvement in sound quality? I've been doing some light reading, and have read up on some preamps the Copland 305, some CJ units...regardless of what I buy down the road, it will be used. Can a Jeff Rowland concentra or SimAudio i5 really keep up with most separates? I've been told by a few people they can. I'm not sure if it matters but the source is a John Wright modiffed Museatex DAC/transport combo.

I like the idea of simple one box solutions, not to mention the money saved on wiring. But a few people on this forum have told me if I like the sonic signiture of the LSi speakers, perhaps maybe it's time to look at getting a dedicated amp/pre-amp for further improvements, if thats the case which should I get first, the amp or preamp?
lush
it is all combinations, but I am going to disagree with the above, I have found a bigger difference in preamps, althought I have heard big differences in poweramps,but the pre amp comes before the amp, so its sonic signature is going to be there no matter what amp you hook up to it. BUT the are a combo so both are very important.
IF YOU ARE NOT INTO TUBE S.E. AMP AND A FULLRANGE SPEAKERS,THEN YOU ARE MISSING A LOT.TRY LOWTHER YOU WILL NEVER ASK FOR ANYTHING ELSE.
Preamp over power amp. I am not that familiar with your equipment. However, as a rule of thumb... A Preamp upgrade, whether it is a stand alone component or within a higher quality integrated, is the fastest way to the pot at the end of the rainbow (At least in my experience).
The right preamp CAN make an astonishing improvement . To comment on a reference to Totem speakers above , i have found every model the company makes to be smooth and grain free . There is not a dud in the entire line .
In my extensive personal experience, the PREAMP makes the biggest difference sonically.
They all sound vastly different, and they can make or break a system.
I have had more frustation over the right preamp than any other components in my system, by far!
Power amps can also make or break a system, but not to the degree that a preamp can in my own personal experience.
The only other component that can make as big, or bigger, sonic improvement than a preamp, IMHO, are the loudspeakers.
Just my 2 cents.