Hi i have platinum audio bookshelf monitors that do not sound right...

OP
I think he needs go for 10 years minimum for sure!
I understand your thoughts and certainly give the Krell a try, just I have found over the years some items when gains do not match up perfectly I have had the volume up too (80% on one combo I remember) and as it sounded ok to my ears I did not lose too much sleep over it.
Let us know how the Krell works out, I can always give it a home if you are really struggling....lol

What is it with all these people around here who happen to have rich friends who can toss them a Krell they have lying around or a set of Nordost Valhallas they do not use.
I must be moving in the wrong circles methinks!
Luck to be given a 3 day old half eaten cheeseburger!

Seriously those Platinums just need some more current to kick into high gear.
One thing you did not mention though, even though you say you need 3/4 preamp volume to get the output you desire what does it actually SOUND like at that?
I mean if you like it, the amp is not clipping etc then there may just not be an issue at all. Or not an issue that requires fixing at this time.