best bookshelf speakers for < $2000?


I have Studio-20 V5s on stands right now for my living room 2.0 music system and, while I like the sound, I need more bass extension.
I don't want to add a sub due to room clutter concerns.   So, I am looking fro an upgrade from my Studio20s.
I have been looking into towers but now am thinking, why not stay with sand-mounted speaker since I have the stands already.   This is for 2ch music only.  My amp is Emotiva UPA-2 SS amp.

Would I do better to go towers or go higher-end bookshelf speakers?


The towers I've been looking at have been 
Salk SongBirds/Towers
Ascend Sierra Tower
Silverline Prelude Plus

Thx.
albireo13
Its tough.   There are so many speaker companies out there that it makes me dizzy.  I bout my Studio20s after listening them at a shop.  It was the first hogh quality store I had visited and they sounded the best in my budget.  
So really, I dont know if I am missing something compared to other speakers.  
I have a pair of Paradigms down in the basement.  They can be decent with some NAD gear, but to me the Vandersteens up and down the line are special.  It's the first order crossover and they are phase correct (the 1's are a bit different, but still awesome).  I hope you have a chance to get to hear them set up properly.  Again, there are others too obviously.  Get out and listen and don't just buy right away.  Where do you live?

Well I think I will stick with bookshelf speakers. I will likely end up in a smaller room and think I can get te more articulate, intimate sound from bookshelves. 
My budget is $2000  my short list includes: 
Nola Boxer 2
Sierra-2
Vapor Breeze
Salk 1801


Any other good suggestions?
lots of great monitors at that price; Merlin, ATC, PMC, Aerial, PBN, PSB, Dali...too many to list
Honestly, you should put the Proac's in there.  Their new stuff is very nice.