I have normally asked of anyone looking to upgrade their system, what is it that's lacking ?, what do you want more of ?, what do you not like about the system ?, before I make any recommendations. Have room acoustics been dealt with ? Have you upgraded cables ?. Is your source ( digital flac files ) good enough. You say piano and guitar is weak in the midrange. Have you tried an audiophile recording ( such as a Sheffield Lab, Reference Recording, Chesky, or GRP ( which is just a few of many excellently recorded labels ) ? Or listened to any Diana Krall, or Patricia Barber, etc. These are the types of recordings that will tax your system to do it's thing, to bring out the best, and show the worst. Guitar and piano, in many instances, are not miked properly in the mix, but female vocal is generally better to judge ( ime ). I am very source oriented, as you might tell. Just trying to help, as is everyone else. Enjoy !