The SHL5s will not be optimized in a 10' x 10' space. The performance will be severely compromised even if the room is treated. It may be more worthwhile to ascertain whether the C7s will sound good in the room(rather than the SHL5s fitting that space) as some may even consider the C7ES3 to be too large for a 10' x 10' space, the P3ESR being the perfect speaker for this room size.
In Jeff's 11' x 12' room, the listener will be sitting quite close to the speakers without much(or any) space between the listening chair and the back wall. The presentation will be very different when compared to a setup that is in a significantly larger room. Listening preferences and patterns will dictate which environment will produce better results. Having said that, the general rule of thumb is to consider small speakers for small rooms, big speakers for big rooms. Small speakers can still sound good in big rooms with proper setting up, but performance of large speakers will usually be compromised in small rooms. More problems with the latter, and more effort is required to address them.
When Jeff Day reviewed the Leben CS600, the SHL5s were in a large living room(link below).
http://www.6moons.com/audioreviews/leben2/system.html Due to the nature of his job, a lot of equipment and speakers have gone in and out of the room. He has probably kept the Harbeths(and the Leben) and used them in smaller room since he can't bear to part with these wonderful music makers. I noticed the Leben/Harbeth review was done in February 2007, and the same system is still in use until 2011, or current. Living with the same system for more than 4 years, certainly uncommon for a hifi reviewer.
If all else fails, the headphone recommendation may come in handy.
