I have built a 7.2.4 speaker set up in a room that is only about a meter larger in both directions and it sound amazing, so it can be done
I have a 2 seater recling sofa in there as my wife is quite happy to watch tv with me and even the odd movie as long as we star befor 8.pm
I would plan on lots of sound treatment absorption be the main facter as there is not enough space for diffusion to work
In a small room the sound will bounce off many walls before it quietens down, so you really need to control those first reflextion points
I blocked off the window so i could hang sound pannels and speakers where ever i liked. That was a big help as i was able to orienate the room anyway I liked. either side of the sofa we have coffe tables for remotes bits and bobs and of course our wine glass's

if we had to walk round them to get to the sofa it would be very tight but as it is now we just walk in sit down watch and then leave
I will be adding more treatment in the near future as well as bass traps
my way of looking at this hobby is of course we would all like purpose built rooms with rows of seating with a trinov pre/pro powering some high end power amps feeding some top of the range speakers but back in the real world most of us can not afford that but we can do the best we can with what we have
So I say go for it buddy just rember you will need plenty of sound treatment pannels, and enjoy
