Ugrading B & W Matrix 803's

I have the Emotiva XPA5 that delivers 200 x 5. I am using a Pioneer Elite VSX92THX Receiver as a preamp. I originally was using the Pioneer receiver's amp until my brother lent me his Emotiva Amp and I had to purchase one a few years ago. The amp gave it much more depth, clarity and punch.The system does sound great however I want more and have the upgrade bug. I am thinking the speakers will give me the best bang for my upgrade dollar.
The room is 20x20 with 18' walls. I do like the sound of the matrix 803's but would think after all of these years that I could upgrade them. What they are lacking is low end punch. When I play dvd's or sacd's through 5.1 the low end is there but missing on 2 channel stereo mode.
I listen primarily to classic rock of some form.
I appreciate your input.

Is your goal to optimize 2 channel performance? If it is, I would recommend a 2 channel integrated or pre with home theater pass through paired with a great 2 channel amp as a necessary investment before replacing/upgrading the speakers.

Golden Ear's Triton Two is a tower with a powered sub in each tower. I've heard them, and they sound pretty good. They weren't as crystal clear as I would have liked, but I heard them immediately after listening to Magnepan 3.7's. They would definitely improve the base on your stereo listening. Vandersteen 3A or 5A's would be a good speaker. I would definitely recommend Maineiac's suggestion.

Personally, if I were putting together a system for classic rock, I'd get some of Zu Audio's Soul Superfly's and run them through a Dynaco ST-70 and a Conrad Johnson PV5 and just keep the 803's for the surround setup.