New mains to complement Usher 5.1 setup?


I have an Usher 5.1 setup with S-520 mains and surrounds, S-525 center, and SW-210 sub, currently driven by a Cambridge Audio CXR120 AVR. We will move in a few months to a house with a deeper AV area and I am thinking of expanding to 7.1. The easiest and surest move is to just buy a third pair of S-520s. But, I am open to upgrading the mains to floor standing speakers that will both play nicely with the existing Usher speakers for surround/theater, and provide an upgrade when listening to music in stereo. My budget will be the $2K range, new or used. The speakers will likely continue to be driven by a mid-fi amp for the foreseeable future, so nothing too revealing of amp flaws. Thanks for guidance and suggestions.
bgmanne
Uh, forgot to mention the obvious upgrade to the Usher SD-500 that goes for about $2k/pr new.  Duh.  It’s pretty impressive to be able to get their flagship diamond tweeter at this price level, but then it’s Usher so not really surprised. 
Thanks for mentioning the SD-500.  I have had floor standing speakers in mind, but I should be open to monitors at my price point.  Interestingly, I emailed pretty much the same inquiry directly to Usher's US distributor at the time I posted this yesterday, but have not heard back from them....

I’ve decided to go with a pair of mini dancer 1s. I purchased now with a holiday sale discount, but retailer will hold until I’m ready to receive them at the new house. I’ll eventually return with some comments after I’ve lived with them for a while.

Congrats on some AWESOME new speakers!  Now the bad news — I absolutely FORBID you to drive these beauties with an AVR.  It’d be an insult to them and you won’t hear half of what you paid for.  My advice — start looking for  a new AVR that has preamp outs and a good stereo integrated amp.  Anyway, congrats again on your incredible new speaks!

Now I’m really missing my beloved Plinius 8150i, with the ultimate Galbo mod….