I have a room that is very similar to yours. I cannot speak for rock as I'm not really a fan, but I use very efficient Coincident Super Eclipse III's which I feel are well suited to the room. One suggestion; have you tried bringing your speakers closer together? You may find the soundstage improves. You are probably listening right up against the back wall from your description. Check out this thread for some further input on this - specifically for options on treating the room. I'd highly recommend the Coincident speakers, but I'd qualify that by reiterating I don't listen to much rock. I'd imagine they'd do very well, but you should ask someone who uses them for that purpose. They do well with both tube and SS amplification. I have also used Silvirline Sonatina's and they did work quite well in my room too, and I did like them very much, but I prefer the Coincidents for their fuller range among other qualities. I would check to see if you can get the room working in your favor before you go changing speakers though.
Good luck!
Good luck!