everything sounded great until the upgrade

In short: I loved the sound of my modest system, until I upgraded my amp. Now it  sounds pretty horrible. It went from a warm sweet embracing easy-to-listen sound to knives and forks trying to escape from a bathtub.

So...

1. I can just unplug this new amp (used) and sell it

Any other options? I could upgrade my speakers but I have no budget for that.

2. I could sell the speakers and use money to buy used ones that go with the amp. 

3. Lastly I could change the source, but was it the culprit - to begin with?

btw - the sound of the "new" amp is decent with my turntable, and terrible with my CD player.

(If I wrote brands and models it would throw the discussion into "A sucks, B is great")