benefits of adding a power amp to a budget system?

I had posted in here before about possibly adding a power amp to my budget audio system.

I have a HK AVR 235 receiver (50 watts per channel RMS) hooked up to a pair of KEF Q5 speakers.

I am considering the purchase of an older power amp, like the CJ sonographe SA 250. I would like to improve the musicality, detail, bass response, soundstage, etc, while providing an upgrade path in the future.

I went to a local hifi store to see what they might have, and the salesman told me that adding a poweramp would do very little for me, that what I really need to do is upgrade my speakers, and then consider a sep amplifier.

Is there really little benefit to adding a sep amplifier at this time?