Possible bookshelf upgrade


Hello to all.
Here is my question. In my bedroom I have as my mains a pair of Definitive Technology Studio 55. I am thinking of upgrading. I run these with a Marantz SR5010.One candidate is the Paradigm 15b. So, would I be gaining much doing this? They are in a 5.1 system. My budget is up to $2000. I have heard the Nola boxer, which is very nice. I am just not sure if at this range it would be significantly better. Thankx in advance for all advice.

arthurd
Perhaps a pair of Zu Omen Bookshelf? I own them for my office and they are quite nice. Also, less than $2k.
Bob
Post removed 
There are lots of speakers that can perform well in both stereo and front L/R duties.  The thing is that as you increase the quality of your speakers the Marantz will quickly become a bottleneck for performance, especially in stereo -- which is why I asked how important 2-channel is to you.  $2000 speakers are more befitting of a separate stereo pre and amp or a good integrated.  These can be incorporated into your existing system very easily.  Hope this helps, and best of luck.