Can start here...
Hey Dave, i got your message but i thought i'd write you here. there is not much info on the type D's here. How you got yours for $50 bucks?? lucky you!
I have a room that is 16x16x10ft high. the ST-85 (70wp) is less power than my previous rotel 980 (120wp) but a way better amp. the 70wp fills the room quiet nice. don't think you will have a problem with them being adequate for your room. I have found that they are extremely accurate (possibly to bright with ss amps). i do believe most of the 80's and 90's snells work best with medium powered tube amps. i do not think you will need the rear super tweeter with your amp - of course that depends on your tastes and your room and all the other variations.
i am just now beginning to use the rear super tweeter with the thorens/denon 103wood combo. i however, have a bright room.
you will need to experiment with the exact placement - i began with my speakers about 12inches from the back wall - once i find a generally full sound i begin to tow in ...moving the rear inside corner 1 inch closer the the rear wall then 2 inches closer then back . usually takes weeks. at the moment the rear of the D's are 10inches (inside corner) and 11inches(outside corner) from the rear wall.
Thanks Pete, for the follow up. I was thinking about the layout of my room and your comments. It sounds like the D,s can be set closer to the wall than my Europas which are approx 3.5' from rear wall and 4' frm sides. This provides a near 9' approx equidistant triangle. Similar to you, spent lots a time with distance and toe-in before getting it right. I imagine your room was greater challenge due to it being square. After I get the D,s repaired I,ll get them set up and let you know how they worked out. Again, thanks, Dave