Seeking speaker purchase advice

I am presently running a pair of Tannoy Revolution XT8F, with my Hegel H20 power amplifier (200 Wpc into 8 Ohm, 350 WPc into 4 Ohm) and RME ADI-2 DAC/preamp. Listening to classic rock and classical music CDs and HD tracks (24/192). The Tannoys are very good speakers, but I am looking to upgrade to, possibly, a ribbon tweeter speaker.  Evidently, I am open to any other recommendations. My budget is limited to $4,000 though. 
My listening room as 13' x 21' x 8 ft high, with rugs and some upholstered furniture. 
Your advice would be highly appreciated. 
Find as many under $4k as you can. Go and listen to them.
All else is noise.
While these speakers don't have a ribbon tweeter, the new JBL 100 Classic speakers at 4K will rock your house down.  They are perfect for Classic Rock.

I keep above speaker with ribbon tweeter and ceramic midrange driver as backup speaker for Lansche 4.1(new price 55K).

This one has very nice midrange sound due to ceramic drive and play loud with 10 inch woofers.

If you are interested, then I may sell this one at 4K$.

If you live near Seattle, WA, you can listen to it yourself or may give you home audition for 1 week.

What specifically are you looking to improve upon?  Just saying you want to move to a ribbon tweeter doesn't say much.  I can't believe the only improvement you're looking for is only in the tweeter.  Tell us what improvements you'd really like to have overall.  $4000 can get you some damn fine speakers, especially I'd you're open to buying used. 
Ascend Acoustics Sierra Tower with RAAL upgrade comes out to around $3000 shipped, more for custom finishes.
Or you could replace the tweeter caps ... :)