I would pin most of the blame on the Thiels. In my early audiophile days, I was a Theil owner (mid-80's, model O3A). At that time I was also getting interested in classical music and it became very apparent that the Thiel's would not produce violins naturally - they always had a glare and edge in the top end that was fatiguing. The Theil sound signature continues to this day IMO. In recent years I've had Spendor SP 1/2E's which are very musical (but lack the deepest bass) and now the Vandersteen 3A Sigs which give the whole package - very natural high end, great soundstaging and wonderful bottom end. For less money, the Vandy 2CE Sigs are also very good. So my advice is to change your speakers first. Next, I'd suggest a decent tube amp. Good luck.
Mark
Mark