new at this...which amp?

Your amp should have more than enough power. You should really try to borrow gear and swap only 1 piece at a time until you find the culpret. If everything is sounding harsh when played loudly, you can eliminate the cd & cable (compressed music usually sounds flat, not bright).
Borrow a stereo only amp if you need to just to run the right and left channels to compare to the adcom.
Personally, it doesn't seem to me like your system is balanced. You have shorted yourself with not enough spent on the sources, nor on the cabling. What speaker cables are you using, do you have a line conditioner?

I don't think power is your problem. Your speakers are rated at 89db with 1 watt which is about average. 150 watts should be plenty unless you are really cranking it up. It's more likely that you are amplifing crap up stream, so look there first.

I wouldn't give up quite yet on your Adcom combo. Adcom is usually near the top of the mid-fi range of gear. I am sure there are numberous reviews that should confirm/deny the quality of your gear.

Your DVD player and interconnects would be a better place to start than swapping amps. 100-200 bucks/pr for good interconnects might help a lot. Stay away from silver and go with a well reviewed smooth sounding copper interconnect. A decent digital cable may help as well. A new DVD player would be the next move. Look for something that is well reviewed for sound quality which is sometimes only brushed upon.

One thing you could be hearing is the compression inhearent on DVD recordings. The quality of DVD sound will become worse (compressed, muddy, flat, etched) as the complexity of material and channels in use increase. As you improve your system, the problems are magnified.(This is the death spiral of hi-fi) Use both multi-channel and simple 2-channel material for testing. Complex multi-channel material can hide problems and confuse your mind about what really is going on. Use material that you are really familiar with.

I found this quote on the net from another B&W NT9 speaker owner;

"I had to sell these speakers due their brash, hard and uncomfortable sound. i tried changing other components to see i could take some of it away, going to the length of buying o 300 watt krell, but they fundamentally stayed the same. there was alot i liked about them - presence, detail, soudstage focus to name a few, but they were not easy on the ear, especially at higher volumes.
i used a CDM-7Nt for a while, which was a much more balanced sound."

Sound familiar?

You might be fighting an up hill battle with these speakers. Armed with this bit of info, you might try swapping your rears to the front and see if you draw the same conclusion as above. Do an A/B test with music and movie content with front 2 or 3 speakers only. If they have the same mid-tweet combo there may be no difference save for the bottom end. If this does the trick, another pair of 7nt's might be the solution.

A few more easy tips:

Leave your amp on 24/7. Most amps sound better (more open) if they are on for more than an hour.

Speaker "break-in" may be an issue if they are new. Make sure you have lots of hours on them.

Plug your amp directly in the wall. Eliminate cheap power strips!!! Get a decent power conditioner for your DVD and pre-processer. These components need clean filtered power for SMOOTHNESS. Amps need current for dynamic power. You can always use a power conditioner even if you upgade components later.

Try this test. Plug-in only what you need to make the system work (eliminate power strips) and see if that makes any difference.

Having owned the B&W CDM9NT they can be a little bright (Not harsh) unto them selves.

I purchased the 9NT to set up with an Adcom GFP 565 and GFP 555. Due to problems with the Adcom gear as it had been sitting in storage for a year and a half, I changed to a B&K Pre and a B&K ST2140. 140 watts was pleanty of power for my needs. I had my Adcom gear for 12 years in that time it gave me excelent service.

That said system synergy is of utmost importance.

1) I would seriously consider upgrading your CDP. Garbage in garbage out. Your reference to harshness is also a little vague but I am guessing that it is the highs not the mids or bass. This is more than likely digital glare caused by a lesser quality CDP.

2) Although I think a cable upgrade would help your system overall, I don't beleive that it will cure your problem of harshness. With the 9NT I have had good luck with copper cables. Silver can be a little brighter in the highs due to its better high frequency response I recomend staying away from silver with B&W speakers.

3) The room is also a component even though you have had the system in three rooms have you ever used room treatments. Again I will mention system synergy.

In closing demo differend CDP's in you system first. It can't hurt and you may find that is the answer to your problems.

Michael

Me too...sort of. My suggestion is the same as many here have offered. Check the cables you are using. B&W speakers- regardless of what you think of them, are really revealing of the contributions components bring to a system. I Love this about them, even if it has meant a little more experimentation. I am not familar with the 9nts models, but I have 1nts. My own experience has been that they can sound harsh when under- powered or when at the receiving end of a bright source or interconnects or cables. They sound bright where brightness is evident! In my system they do not sound the least bit bright or edgy, and they have given a much better account of recordings than I got from the their 600 series sibling... and this from a system I would consider less capable than yours.Really, I wonder if just changing out the Denon source for anything else for any amount of time wouldnt serve to show you the difference a little change could make?

It's really hard to get so much advice, isn't it? Maybe more than you bargained for! The difficult thing about audio is that all the individual pieces have to work together. If you are like me you put together a system one piece at a time, when you could afford it. Some of the best advice I ever got was this: the speakers are the most important device because they produce the sound waves that travel to your ears and they translate all the electrical signals (good and bad) into sound. The next most important piece is the source component,in this case the CD player because this is the beginning of all the electrical signals. GIGO. All of the other pieces are of diminishing importance compared to these two. That is where you want to spend your money. In my view, the following pieces fall in order of importance: speakers, source, pre-amp, amp, interconnects, speaker cables. Each one is dependent upon the other. My Classe CDP is not the most expensive, accurate, revealing or detailed, but it allows me to forget that I am listening to a disc and it sounds so beautiful. My Dynaudios allow me to forget that there are speakers there and I can listen to them for hours. After all, its only about being able to listen to music and forget about all the equipment in front of you. Turn the lights off. Do you like what you hear?