bryan, i understand what you are saying. but, it has been my experience that, in a compromised room - like one as small as 10.5x10.5 - it is better to set up asymmetrically, to even out room nodes, then to worry about image stability. while i understand you want the listener out of any node areas, it is good to reduce the nodes, regardless of where the listener is. you can get a stable image by being somewhat nearfield, and by absorbing 1st reflection points. this has been my experience and that of others. is it perfect? no; hard to get perfection in a wery small room; everything will be somewhat of a compromise.
regarding subs; i think one or two smaller subs - could be 2cu-ft or less - would be more than sufficient. you're not looking for ultimate sub-20hz response, only enough to smooth out room nodes. this is one case where i would allow the mains to run full-range, instead of crossing them to the subs, to allow for more sources of the low frequencies...
ymmv,
doug s.