REL subs--Strata III or Storm III ??

The Storm is not that much bigger. It is the same width and depth; and only 4 inches higher. It weighs 15 lbs more. The extra 50 watts of power are worth it in my opinion. That and the design lets it go lower. You could read the HiFi Choice Magazine reviews online of both. They also preferred the Storm between the two. They liked them both overall. (So do I).

I have a Storm III sub, which I auditioned against several other ST series subs, including Stadium and Strata. The tough part was the speakers it had to 'mesh' with - Martin Logans. Electrostatics are very fast, and subs tend to have a hard time working well with them. I just kept coming back to the Storm as my favorite. It literally disappeared as a separate sound source. It also had excellent depth and smoothness on top of it's speed.

Of course YMMV, as you have very different speakers to work with. The bestest recommendation is to hear them each setup with your speakers in the SAME environment and physical orientation so you get a real comparison.

I didn't like my Strata II. It didn't seem to go low enough, and the sound was pretty boomy. I wound up trading it in used to the dealer. I guess the Storm III is better, reading the reviews. I recommend you try listening to both, at home if possible.

Just a comment; a Stratus II only has a 60 watt amp, and has a different internal design than the Stratus III, which other than the name is a totally differenct sub.