B&W 805s vs. 705S

Yes. About $1000.

I think the CM1's are better (except for bass and perhaps(?) some dispersion characteristics) overall, imo, than the 705's, but if you like either of these two units, the 805S's ought to be a real pleaser. I have some customers that kept upgrading across various differant brands/lines till the got them and have since expressed no desire to change (same for some with the older N or Sig 805s). My wife gave me an unqualified "get them if you want them" after listening to the Brandenburg Concertos on a set at work while waiting for me to return one day. My wife is usually CHEAP too.

I found the difference in price between the 602s and 705s worth the price jump, but the difference between the 705s and 805s not. I also prefer the 705s to the CM1s because the imaging is better and they have enough bass to be used without a sub except for movies and pipe organ.
Are the 805s better? Yes. Are they $1000 better? No.

Neither is terribly hard to drive and have similar characteristics so I wouldn't worry about that.

I run an 804s with 135 Watts per channel with no problems. Even at loud volumes, the amp is barely warm to the touch. This being a Rotel RB-1070 fyi.

The 805s is a better speaker than the 705, but the jump is not as large as 602 to 705 for instance. The difference is real though, and imho, worth the price jump to me.

I went from 602 to N805. I had originally planned to get 705, but N805 was phasing out and I got it for 150$ more than the 705 costed. The N805 was better than the 705 in my opinion in terms of overall clarity, and dispersion of treble; and then I jumped to the 804s and am very content right now.