the better the components the more they reveal the shortcomings of the system/room interractions. Your best bet aside from treating the room if that isn't possible, is to get speakers that sound less forward and less bright. I don't think preamp will help reduce overall brightness, although a tubed pre may decrease it to some extent, but it won't satisfy you in a long run. To me a change of speakers is the best solution.
JMO.
JMO.