So how many people are using subwoofers

I love my sub,it's addictive. If you crave bass athority get the sub, or better yet get two!

I would go for the amp change, but not necessarily with a higher powered version of the same solid state amp. Consider an OTL (the Joule sounds great with your speakers) or maybe Rogue monoblocks. My main speakers go down to 35hz and while I could always use more extension the bass output is more than satisfactory.

Since you specifically mentioned "bass weight" and not bass extension (the Sonatas go low enough) the sub may cause more problems. I've never heard a system with subs that sounded seamless, unless it was designed that way (Pipedreams and Airfoil come to mind, but they use multiple subs). Full range speakers are usually the desingers final statement and simply adding a sub is not that easy especially if the main speakers are ported.

I run dual Rel Stentors. You would be suprised on how much it will add to music. It will be fuller and smoother with better imaging and seperation.

I recommend changing the cabling while your at it. I use Mit Reference in my system. I noticed more bass from the minute I upgraded. When you use MIT It is recommended through out the whole system. IMO their quality cables don't even start until you get to the 750 line minimum.

No contest, get the REL. You have no idea how much you're missing, and any amount of words we can say here won't even begin to describe the improvement you are in for. The only people who aren't gaga over RELs are those who haven't gotten them yet or who haven't bothered to spend the time to get them broken in and tuned properly (both of which take a long time). Suggestions: 1. get the biggest REL ST series you can afford, the performance goes up dramatically with each and every step up. For me, one Stadium is the minimum. 2. On a performance per dollar basis, get one bigger one rather than two smaller ones. In other words, one Stadium will significantly outperform two Stratas if you can find a location for it that gives a smooth room loading. Of course, on an absolute basis, two is better. 3. Set the crossover point a LOT lower than you think you should, typically by half an octave or more. If your speakers are good to 45 Hz, start the sub at around 30 Hz (!) and play with it from there. Good listening!