Used 804 N or S vs New CM10 S2?

Well, I would consider something other than the B&W's...

804s will be too revealing for this system, can't recommend them. CM 10's are nice. Will be curious to hear if Adcom sounds better than your Marantz as a preamp. A friend was recently looking at the CM10s and decided they liked Focal's new towers better. Food for thought.

Well, I have the Rotel 1090 amp coming later this week along with the Adcom preamp. Currently they are hooked up to 683 S2's so I'm not sure how much of a difference I will hear compared to the Marantz as a preamp and the Adcom GFA 555II as an amp. Will have that section of the system switched out later this week so I will see. Speakers seem to be the next logical upgrade...

Sorry I didn't chime in sooner, but didn't think you were going on an electronics buying spree so soon. I would have recommended choosing the speakers first, then choose an amp that has the appropriate power and sonic traits that match well with the speakers and your sonic preferences. And same for the latter with the preamp, which IME and in my system has a greater impact on sound than the amp although YMMV.

B&W speakers are fine, but there are lots of excellent speaker manufacturers out there so not sure why you're focusing only on B&W? If you haven't yet had the opportunity to listen to some other speakers I'd make that priority one. Getting that perspective is critical IMHO to be able to choose speakers that are truly a good fit for you. Other than imaging and soundstaging I don't recall seeing what sonic characteristics are most important to you so can't really make any other good recommendations at this point. I will say that if imaging/soundstage are important, brands such as Joseph Audio, Vandersteen, Reference 3A, and Silverline (just to name a few off the top of my head) are some speakers you should try to hear. Anyway, just my 2 cents for whatever it's worth, and best of luck in your search.

I'm going to listen to some Vandersteens today actually, but I had to start somewhere hence the original question and since I have had the CM10's in my house, I thought I needed to start with something. Not sure I fully intended to get into this, butI am now!

I did know the Adcom amp was very temporary so the Rotel 1090 was an easy upgrade and was only $700. I also wanted to see if I would find much difference by going to a preamp from the receiver and the Adcom pre was only $150. I'm selling some other items so I actually have money left over from that and if they aren't what I am looking for, I think I can sell them for close to what I paid.

Basically, I wanted to get a "system" together and try to get a good feel for all of it and then work out differences as I go along an upgrade path.

However, I do know for certain that the 683's I have now will need to go (just received an acceptable offer on them) so I figured that would be the best place to start trying to get some advice here...

Hopefully that makes some sort of sense!