Looking what you have, I'm not surprised that violins sound edgy or bright. Some of your components are good quality (speakers and amplifier) but "oddly combined" like the McCormick amp and NAD preamp, while others more pedestrian like the 12 year old Marantz CD changer! With all do respect, violins and pianos will only sound natural when using higher quality source components. And to sound really good, the system should be carefully assembled through trial and error, selecting based on what you hear rather than what a reviewer says.
If you are serious about improving the sound, find a good audio dealer or two willing to loan you several pieces of equipment for home demo.... at the same time. Start with the source and amplification (pre & amp) first, leaving the speakers and cables as your "control". The Spendor "house sound" is definitely NOT bright and favors classical and acoustic instruments (I've owned two models), so keep the SP 1/2E. Integrated amplifiers have vastly improved in recent years, and are a good (preferred?) alternative to modest priced separate amp/pre-amplifer combinations from different companies. (It removes some of the uncertainty.)
On a personal note, last year I revamped my entire audio system after moving to a new house. It was a fair amount of work borrowing four high quality integrated amplifiers (Rega, Sim, Naim, etc) and speaker sets (Quad, Dynaudio, Totem, etc.). But the result is amazing... clearly the best, most natural sound system I've ever owned. And yes, the violins have body, warmth, and tone that sound very real. Same with piano and trumpets, too.
