Ugrading B & W Matrix 803's

The 803's are worth around $1600. My dad recently picked up a set for ~1000, but you should be able to expect more.

As far as new suggestions go, it really depends on the rest of the system. What's your setup?

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.