2 REL Storms or 1 Stadium?

The Stadium 3 is an excellent subwoofer. I think they are so good that I purchased a pair. I have absolutely no regrets. Would I have better sound with a pair of Stentors, you bet! But I imagine if I had bought twin Stentors, I'd then be lusting for a pair of Studios.

My room is 15x16. Do you feel the Stentor will be too much for this sized room? I hope not!

A couple comments:
1) Don't worry about room size, either will work fine in your room. You're going to have to spend some effort on placement, though, since your room is pretty close to square. If it has 8' ceilings, that's a pretty bad situation for standing wave problems as it is almost exactly 1:2:2. This will cause problems in the lower end of your satellites as well.
2) IMO, the Stadium is a bigger step up from the Storm than the Stentor is up from the Stadium (law of diminishing returns begins to kick in here as everywhere else). This is not to say that the Stentor isn't worth it; I think it definitely is. But the Stadium is still a very good sub.

Karls,
That's true, that's exactly what the dealer had told me when I was evaluating both subs.

Sea2,
As the others have said in this post the Stadium is awsome go for it! You will notice the difference as soon as it starts playing. You could use your present subs position to start with as a reference point? Also consider the XLO cable from the cable company it does improve the bass even more.