what do I upgrade?

I agree with several other posters above regarding the dedicated circuits/lines and line-conditioning.

However, I would specifically suggest Foundation Research LC-1 and LC-2 line-conditioners. These are both passive (no current draw onto themselves) and dedicated to one per component (what else would you use with dedicated lines?) and bi-directional filtering (mandatory for those with a digital source).

In addition, I would suggest some serious experimenting with vibration control ie de-coupling v. coupling racking systems, speaker platforms, etc..

Without properly addressing the these absolutely foundational issues, I believe it is simply impossible to realize the full potential of any system.

-IMO

Not to be repetitious but I would also go with dedicated lines first, you're happy with your Red Dawns?--stay with them, if not you can certainly do better, then, power conditioning. I'm a big Audio Magic fan, but you can do Shunyata, Sound Application, and others, as well. I treat my electric as another component. Those three steps will give you electric nirvana. Your system will thank you for it. peace, warren

My first thought is the Red Dawn may give the 'light' sound you speak of. Of course YMMV. It seems to be average cable for such a nice system.

I agree with the posts above, dedicated circuits and power conditioning, including room acoustics. I would add high quality AC outlets such as the cryo'd Porterports sold here on Audiogon (one of my favorites).
Secondly, if you changed your interconnects you most probably will hear a big difference in what you stated you wish to improve. I have been most impressed by the interconnects and speaker cables made by Ridge Street Audio. They work very well in my tube and SS systems.

Dedicated circuits: if you had done this to begin with your upgrades would have been more enjoyable along the way, AND PROBABLY NOT HAVE SPENT SO MUCH - BASICS FIRST!!