new equipment power conditioner or more powerful amp?

I would add a dedicated line first. It shouldn't cost very much, either.
Bob

To get the best sound from your system you need to:
Get Jim Smith's book Get Better Sound,
Follow the instructions,
Dial-in your setup,
Apply room treatments where necessary,
Enjoy your much-improved sounding system.
The room and setup will contribute AT LEAST half of what you will hear.

Tom

Agree, tweak the system setup and then the room. 

For $1-2k you could buy enough Blue Quantum Fuses, ECTs and HFTs to have your system performing on a level far beyond anything you could get from any new amp on the market. This stuff is seriously transforming, most of it you can try 30 days and return if you don't like it, and best of all you buy it once and use it everywhere forever from then on.

My 2 cents... improve your power by installing dedicated AC lines; cleaner power which will provide a lower noise floor.
Next would be room treatments, they don't have to be expensive. Then you'll hear the true sound of your current system.

Spend about $120 on a Furman power strip like this one:
https://amzn.to/2TkbFtj

And the rest on room acoustics.

GIK Acoustics and Michael Greene Audio are good places to start.