new at this...which amp?

Adcom is decent stuff - I doubt whether you'd hear any significant difference with a Rotel. Amps are not where your problem is. What's your front end?

150wpc should be enough power, and changing the power amp is one of the last things I'd do - negligable if any return on $ spent. Adcom's are OK, and adding power would only exacerbate the situation.
Brownsfan has a good handle on a good way to tame room / system interaction. If you look at the pictures of my system you can see that wall treatments are used heavily to tame the sound - I can go MUCH louder on my system than before before it glares at me from room interaction. Spending $200-$400 here will make a ton of difference.
Another place to look is your front end - what's your CDP and DAC? Harshness and grain are typical digital factors. You may not notice it as much at lower volumes.
Don't get carried away on cables yet either. sure I'd do somethuing a bit better in interconnects, but again, value for $ spent will be room treatments and digital source components. I usually vote for Transparent cables, as I think they affect the sound the least - ever notice they're never mentioned in cables to make the sound change threads? But even so, cables are a small change compared to the stuff above.
Don't think about changing amps until you have the things above considered.

How to fix a room - www.auralex.com. Send a drwaing or picture of your room with dimensions, openings, etc. At no charge they will make recommendations on what you should try.
Amps - In order to get twice the volume, you need 10x the power (sound is logrithmic). Doubling of the power will supply a "just-noticable-difference" in sound volume.
You don't want to be going into the complexity of bi-amping, when you have enough of the fundamentals it appears like you need to take care of first.
The easiest way to get loud and clean - get more efficient speakers.