That is a perfect size room for M60s! You don't need HP drivers. Use the money you save for QS10s.

I had M5s in my 4200 cu. ft. room, 12 feet apart and I sat 14 feet away. I loved them! Far better than my M80v2. The M60 non-HP will be just as awesome. According to Ian, M60 is the way to go over M5 unless you absolutely must have bookshelves.