Adding pre-amp to an integrated amp?

I am using an tube integrated amplifier. From some immates in a newsgroup in Hong Kong, they mentioned the addition of a pre-amp. to the integrated amp. (treat the integrated amp. as standalone power amp.)and its performance improved. Does it make sense to amplify the signal twice and resulting in better sonic performance? Hope the immates here to throw me some light on this.

Perhaps this it what they are referring to; some integrated units have a set of U-shaped pins that can be pulled out. When that occurs the amp/preamp can be used independently of each other. In that case, a better preamp could result in better sound.
I agree with LAK. I doubt they are double processing the sound. Some integrated's also have an additional pre-out so you can add a second amp and Bi-amp using an integrated. NAD, Cambridge Audio, and Rotel's for example.
Nope. They are using the same integrated amp as mine. It don't have a pre-out. To my understanding, the immates just plug the output signal from the pre-amp to any of the inputs of the integrated amp. This resulted in double amplification of the signal. That cause my posting of the questing.
Siulau: Are you using an amp that only has a single volume control (the only control on it) and which only accepts one line source? Better yet what amp are you using? I have tried a few active preamps with my Audion Silver Night stero 300B amp (which has a single volume control, an Alps, and that's it). I tried setting the volume on the amp at between 10:00 and 2:00 on the dial (which should be its optimal range) and got different, but not better sound. I seemed to lose the micro details of the amp (on its own) in exchange for added flesh, dynamics and a slightly wider sound stage (which may be what you are looking for). I had thought that because of this I may want to try a passive preamp next (though I cannot afford the ones that look good to me at this time) to see if one would make less of a change to the sound of the amp. I would like to add switching capabilities (like add a CD changer for my wife to use and maybe even a turntable at some point) which is why I even tried the preamps in the first place, so our goal is not the same. I do not really consider the Audion to be an integrated amp, just a power amp with a simple gain control (volume pot). The pot itself may be passive for all I know as I do not know much about the design of the unit.
Thanks for the inputs from all the immates. I have also post the same question to the immates and they finally answere me. They said the so called integrated amp is in fact a power amp with input selectors and volume control.