amp or preamp to extend upper end


I went from a fantastic little Krell integrated amp to a Musical Fidelity M6 amp and preamp. Found that the high end is a bit rounded off -- that amazing detail I had on the cheaper Krell is lost. My dealer said that the owner of Musical Fidelity designs his equipment for this sonic signature intentionally. Maybe I just got to used to an over-emphasized high end.

Question: would replacing the amp or preamp have a more noticeable impact on extending the upper range (assuming the new equipment can do so)? Any suggestions? Speakers are Vanderteen 3s.
evolving
LOL - I thought it stood for "Bring My Wallet" I drove three 80's cars into the ground '80 320i, 83 325 & 87 535is & the best a '95 R100RT (2 wheeled airhead variety) until I totaled it 2 years ago. They were all great machines in that era & I had a good independent enthusiast mechanic for the maintenance I couldn't handle myself but he adamantly said stay away from the newer stuff - electronic nightmares.

Fusion handling better than a modern day Bimmer - yikes!

I used to date this Russian girl. She told me there were only 3 letters in the Russian alphabet: BMW.
"I'm confident on all models upto 2007. Parts are not overkill and work on any repair is faster than in any Toyota or Honda.
Expensive maintenance prices only for the fact having european luxury car."

Parts are not overkill??? You must be joking. You must live in Germany or somewhere in Europe. Here in the US they are absolutely absurd. A Euro luxury car shouldn't have to be synonymous with frequent electronic failures and absurdly expensive repairs. If European luxury continues to equal frequent expensive maintenance their allure will eventually wane as others close the gap. And this from a big fan of German cars.
I think that there has been a lot of variation over the bast 10-12 years. My wife's 2002 325xi had an ongoing electrical problem but was one sweet driver. Felt like it could rev forever. She traded in on a 2011 328xi that was sluggish and the run flats were hard as rocks. She dumped it for a 2015 A3 that is one sweet car w low end pull like a V8. I just bought a 2014 X-1 that is pretty darn nice. Of course they are expensive to maintain but the new ones have maintenance included.