HT surround speaker selection

[klettermann]

The new media room is waiting for carpeting. In the meantime I'm getting stuff out of storage and ready to install. The room is W12." x L22' x H7.2ft. It will contain a single couch and be used overwhelmingly by only 1 or 2 people. Today's question is rear and side speaker selection. My general path is to get 2ch and 7.1 up and running (placement, acoustic treatments, etc). This will be a dual use system for both video (7.1, maybe 7.2 etc) and 2 ch audio wherein the fronts will do double duty for both. Installing Atmos height speakers for 7.x.2 or 7.x.4 will follow later after 2ch and 7.1 is dialed in. The fronts are already decided, Magnepan MGIIIa's - ancient but recently factory rebuilt to better-than-new. They were the predecessor to the more familiar 3.7 family, so placement issues are about the same and I've got that covered. Less clear are what to use for the side and rear speakers. Here's the selection:

• KEF LS50's (bookshelf),
• MG Quart Ones (older bookshelf but quite capable)
• Maggie SMGc's (essentially same as the newer MMG's)

IOW, pick 2 out of 3 for sides and rears. I guess there are various ways of thinking about it. One school of thought is using similar or identical speakers all around to the extent possible and practical. Given my grab bag that could mean using SMG's (most similar to fronts) and one of the bookshelves. And, if this, use SMG's on side or rears? Or, use both bookshelves (most similar to each other). Every possibility has pros/cons regarding placement, aesthetics, etc. Presumably you'd put the best stuff where it counts the most, but I don't have a very good grip on how much info typically gets to the sides and rears. My inclination SMG's in the back and one of the bookshelf pairs on the sides Are LS50's overkill for just side speakers? Another possibility would be just sticking with 5.1 and just making it an all-Maggie system. I'm sure there are all kinds of other considerations as well.

As some wise man once said, "Do what you can, with what you've got, where you are." So, to be clear, these are the speaker choices. Please let's not suggest other choices, starting over, etc etc. Also, I will move things around, so no reason for "put it where it sounds best." What I'm looking for are pros and cons of respective placement scenarios. Looking forward to ideas and comments. Thanks and cheers,