REL subwoofers...old vs new

I purchased a REL Storm III new about 10 years ago. It has blended seamlessly with a number of mains that I have switched in and out of my system. I am pleased with it's performance but considering the age of the sub and some of the newer models available I am curious how the older Storm would match up with some of the newer R and G series REL subs. Has there been any significant improvement in design and/or sound quality found in the newer models that would result in a noticeable improvement if I were to upgrade? Just looking for input from those who may have compared older REL subs to the newer models...your impressions.
I had a number of people recommend that I go with an older bulit in the UK ST model (ST=Strata, Storm, Stadium) over the comparably priced newer T models. But I was limited to the under $1000 price point. If you are only running one sub, you might also consider going with dual Storm IIIs, to help get a more uniform response in your room. If this interests you, slap onto my user e-mail and send me an e-mail. I've moved to floorstanders that go to 20 Hz and am no longer using my REL Storm III.