new at this...which amp?

I recently got pretty tired of dealing with harsh and strident highs with my system. In my case, it was pretty easy to narrow the cause down to room resonances in my new house, since I had recently moved and had not made any equipment changes. Before you spend a lot of money on equipment, you might want to rule out the room as a cause of the harsh sound. If you have something that will absorb or diffuse sound to put in the corners it should give you a clue if this is what is going on. In my room I put about $110 into some Auralex studiofoam and used it to deaden the corners and it made a world of difference. Lots of dealers that sell musical instruments carry this stuff for people who are setting up recording studios.
If you have a really good audio dealer near by, talk to him about your problem. He may let you borrow a demo amp to try for a few days. If you try another amp and still have problems, I'd keep working on the room.

Sell the Adcom amp, and buy an S-H2O Signature for $2800. If you want to know why, read the review at 6Moons. Replace your Radio Shack interconnects with used anything at Audiogon.

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.

I second the post from brownsfan. The room is very important-taming resonances, toning down harsh reflections, taming bass modes, etc. I had an ADCOM amp and sold it. I thought it was too brilliant on the high end, and that was a "soft" room. I really don't think its a power issue, but more of an amp issue. I bought Outlaw M200s for each channel and they really "disappear". I don't perceive any harshness or ear fatigue. I think there are many amps in your price range that you would be happy with, but, again, you may want to work on your room first. Good luck!

Not so sure it is the room. This system has been in three rooms and had the same problem.
Muralman1, is that to say that Adcom is not good stuff? I have a Rotel 200 by 5 available to me at a good price. Is that a better choice than the Adcom 300 by 5? I will look at that review for the Signature.