Best Upgrade you had?

The most cost effective upgrade I ever made was dedicated power lines.

Ok, If we're talking cost effective: I agree with Stage.

For cost effectiveness top flight cans can truly bring out the best of your system without paying exteme dollars for speakers then spending weeks tweaking with room treatments. Also good for isolating what part of the system hums, needs improvement, ect. Followed by dedicated headphone amp with conditioned or battery power supply. IMHO of course.

The addition of a subwoofer intended primarily for HT. I've found that a few work well with movies and music. I listen to 2-channel daily with a REL Stadium III. A good sub that is intended for music will make a significant improvement to anyones listening experience. I'm hooked.

replacing my Anthem PVA2 poweramp with a CJ MF2500A has made the biggest improvement to my system,as good as the Anthem is for the money,the CJ has taken my system to a much higher level,cant wait to hear how the Supratek Chard. i have on order is going to sound!!!