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.