The biggest (no soldering required) audio bangs for the buck, in no particular order:
BDR Cones under everything.
BDR Pucks, Those Things, Shelf under everything.
Synergistic Research HFT, ECT, PHT throughout your room and system.
Cable elevators to get your speaker cables and all other wires up off the floor.
Anti-static spray. Pay through the nose audio prices or whatever you find at Safeway, either way just spray it.
XLO Calibration and Burn-In CD: play the demagnetizing tracks at least monthly.
Radio Shack bulk tape eraser. Works on things you'd never expect or be able to explain, like CD's.
Felt pen, Sharpie, or paint pen edges of CDs.
Scotch tape, dress interconnects.
Tape measure, framing square, laser level. Only takes a tiny speaker misalignment to undo even many thousands of dollars worth of components.
Radio Shack SPL meter. The cheaper analog one.
Best of all, unlike the mega-buck component you've been conditioned to want so bad now yet which will in no time be found wanting and traded off just like you're doing right now, pretty much all the above tweaks will work just as well with anything and everything, forever.