Any advise to improve my system

Patrick, I'll take a shot. Here's what I'd do starting with the least expensive. Try a mit 2 power cord on your amp, the SR master on my classe makes the soundstage thick, slow and creates a mid bass hump that is distracting. Classe amps are high current, and I think Plinus is also, that's why lots of Classe and Spectral amps are demo'ed in stores with mit powercords. I use the SR masters on my digital front end and they are superior to the mit in that context. Next, I'm a big mit fan but based on my experience ic's and speaker cables should match to really get the benefit of the coherent sound you get from all mit. Go for 330 shotguns or better if you can swing it - used. I would live with that change for a few months to let everything settle and burn in. Next, If not completely satisfied (who ever is in this hobby), I'd look into a tube preamp. Good luck...