fruckman wrote:

Would it be a mistake to buy speakers that due to their height require being placed on their sides (i.e. Harbeth C7ES-3 or Spendor SP2/3R2)? I realize this would not be ideal, but think it may be a better match for the room. Thoughts?

Generally, it is a really bad idea. First, almost all floorstanders (there are rare exceptions, such as Linn) are designed to and do sound best away from walls. Second, almost all floorstanders have their drivers vertically-arrayed in order to provide proper horizontal dispersion essential for stereo imaging.

To be complete, very few "bookshelf" speakers are meant to be placed on bookshelves, anyway. So, if you cannot put speakers vertically and/or away from walls/shelves, you are encumbering major compromises in performance.

fruckman wrote:

I understand that all of your points are correct. However, I will be placing bookshelf speakers on bookshelves. What is your advise that will be helpful in getting the best result from my specific setup?

Keep them vertical.
Place them with their front surfaces flush with the front edge of the shelf.
Fill any of the flanking voids with books, records, etc.