Which Budget Friendly Floorstanders Next?

I'd address the preamp first.  The preamp is a very important part of what you ultimately hear, so I'd recommend a good stereo pre first before changing what are already very good speakers.  Best of luck and FWIW. 

Has anyone heard the Revel F35 or Fluance Signature?  Both very cheap, well made speakers.  Can't help but wonder...

Revel F206 used

Again, I don't know much about these Revels.  The guy who sells them by me was a real dick about them.  

I walked in and said I was looking to replace my Monitor Audio Silver 6's and was looking in the $2,000 and under range.  He brought me right over to the Revel F36s and said bluntly "Well..  These are the best speakers for under $2,000 that you can get.  Everyone that works here has a pair and they're great.".  He had the F36s and some other speakers hooked up to a Denon receiver.  He sat me down in front of them in some nice leather chairs and brought me an RCA to 1/8inch wire so I could play some of the tunes from my phone.  (Unfortunately I just happened to be in the area and was unprepared).  I listened to David Gilmours "The Blue" and then Iron & Wine "Caught in the briars".  They sounded full bodied top to bottom, but how could I tell with Mp3s playing on an iphone through a receiver...?

I mentioned that they sounded good but I couldn't get a good grasp on what they can really do because of the receiver and the iphone etc...  He responded by telling me that the Denon receiver was really nice and that it shouldn't be a problem.  So strange.  These guys sell some quality stuff too like Mcintosh, Music Hall, Totem, Martin Logan etc

Anyway..  They are the only dealer around and I had a bad experience, but upon further reading Revel does seem legit.

I just picked up a pair of Kef 107.2's for $1400 and they're pretty damn good! These have had the driver's surrounds replaced and crossovers serviced so they're in pretty good shape, you could probably find a similar pair. I've also got a couple pair of Martin Logans (CLS llz and Aerius i), just sold a pair of Maggy 1.7's and had a pair of Vandersteen 2Ce's - the Kefs are more than capable of holding their own in this group. The Vandersteens are really good too, you'll never go wrong with a pair. There are quite a few older top end speakers available that are in your price range now.