Fishwater,
I know you don't want to go down the sub avenue, but I would suggest adding a Vandy sub if you can fit it into your room.
I don't own Vandy mains, but I do own a 2Wq sub. I have a friend that owns a pair of 2Ci's, which I am currently borrowing. I was listening to them this weekend in my 13'x17' room. My amp (Bryston 9BST) was clipping very briefly and the idiot light in the speakers never turned on.
The sub will take some of the load off of the amp and the speakers, allowing them to play louder and cleaner. Things were quite loud when my amp was maxed out. I don't know how loud you want to go, but it my room, they were pretty darn loud with R&R. I am not sure how much more power the speakers could take since my amp gave out first.
If the 2 Sig's don't really work for you in your room, then finding new speakers is your best approach. If you do like them, give them a shot with the 2Wq sub. It should give you better bass and more volume headroom.