You need to go nearfield -- get some nearfield monitors; this way you will cancel out the effects of bad room acoustics as well as allowing you to get away with lower power. I recently tried this out in a small, cramped bedroom with a pair of Spendor 3/5 (which I think you should consider used) --
these speakers are descendants of a strictly nearfield monitor and so, unsurprisingly, I have found they sound best nearfield--in my case 6.5ft apart, sitting 6 feet away. The sound is smooth, full and balanced with great soundstaging. Volume is not a problem---in any event, I think you should take care not to get speakers that are too big and overpower the room.
these speakers are descendants of a strictly nearfield monitor and so, unsurprisingly, I have found they sound best nearfield--in my case 6.5ft apart, sitting 6 feet away. The sound is smooth, full and balanced with great soundstaging. Volume is not a problem---in any event, I think you should take care not to get speakers that are too big and overpower the room.