I have the 60s in my HT setup and definitely heard an improvement when I switched the fronts to large vs small. The cost of a good second sub will be more than the cost of going from the 20s to the 60s and give you better overall sound for both HT and music IMO. The footprint will also be the same as you need stands for the monitors and will add to the cost.
Bookshelf vs Floorstand speakers for HT????
Since front speakers are generally ran as small, is there any advantage to using floorstanding speakers vs bookshelf? I will be using a sub and this set up will be primarilly for HT. The speakers are Paradigm Studio 20 vs Studio 60's, both are version 2. Any help is greatly appreciated. Thanx Chris.