Bookshelf or Floor standing for ~$900


Looking to get some new speakers and am wondering how my money would be best spent. I will say that I always buy used/demo as I view audio value similar to automobile value. Take it out off the lot or out of the store and its losing a lot of value. 

My room is roughly 14x24ft and the speakers will be along the longer side. 

I've been eyeing some Monitor Audio Silver 100s for $750 as well as some Martin Logan Motion 20s for $950. 

Will two 5in drivers be better than a single 8in? Are there other options you would recommend? more generally (as the title suggests) should I be looking at bookshelf or floor standing speakers in this price range?
128x128kyleeto
What is rest of your system?

What speakers are you using now?

Volume levels?
I listen to mostly alternative and electronic music. Artists like Alt-J, Tame Impala, Glass Animals, Flume

I'm looking for clarity in the highs and a full, dynamic sound. I have a pair of Quad S-2s right now that I really enjoy. The ribbon tweeter does a great job with the highs and the sound is great but I'm interested in something more lively for a second system. 

Would be pairing it with a CXA61 or moving that to the Quads and using a Vena II. 
Two floor standers that can be had used for ~$700 are a pair of B&W CM5s or Dynaudio Excite 14s. Both image well and are dynamic in their presentation. Lively could be used to  describe them. Of course my perception.
elac has some relatively inexpensive floor standers that are well regarded... andrew jones designs