everything sounded great until the upgrade

It appears you liked the sound of your previous amp.  Perhaps sell the amp and replace your CD player with a really nice streamer.  I have an OPPO 105 and no longer use it.  Who wants to get up to change a CD?  I like also my huge library and easy access using Tidal.

Let the new amp break in, sometimes it takes weeks. Never turn it off.

Try an outboard DAC with a tube output buffer.

My Amp doesn't even have an on/off, switch,same said for my pre-amp and Phono amp.

Turing your gear off and on just kills it's life span and doesn't help the sound. I work in broadcast with gear costing  thousands and thousands and thousands of dollars and it all stays on till it fails.

Give it time, you could end up all right.

There are also a ton of inexpensive tweaks that can make a huge difference too. 

Just putting 4 McCormack Tip Toes under my old Conrad Johnson turned  a very good amp into a sumptuous sounding piece of gear.

HiFI tuning / Synergistic fuse to replace the main power fuse, better power cord and AC outlet ( even just Green Dot hospital grade AC cord/outlet) etc are all reasonably priced add on's that can make a big difference.

Don't chuck the amp out yet.

Hope some of these things will help!

@grossman616 

Yes! Very helpful! However, should I really not turn it off? Ever? Doesn't it wear it out?

If it is solid state amp leave it on for a week or two, listen to it or not, at the end of the 2 weeks, if you don't like it sell it and get something else. Don't try to make gear sound how you like it, buy gear and keep gear YOU think sounds good.

New electronics especially transistor / ICs take at least 20hrs of use before the sound settles near what it will be. Tubes seem more forgiving in my experience.  There also could be an output mismatch between the power amp and speakers. I will never forget in the 1980s when my JBL Lancers sounded awesome on a 25w Pioneer  SX525. We borrowed a friend's SX1200 pioneer to try back at home. It way out classed the 25w / ch in every way with if I remember right at least 100W per channel.  In comparison the 25W pioneer blew away the much more high tech SX1250. We were shocked.  The ESS 12" box with air motion transformers sounded great, so did Klipsch horns with the 1250.  It was definitely a component mismatch between the Lancers which sound great with 90% of what was out there.  Lesson learned. Hear components on your system if possible or with a company that will let you demo at home.