At $650, don't you mean "How would TWO of them fair against...?"
See the link above to the Sound and Vision review.
I don't know what people are expecting for $300. I have one and I love it. Would I be happier with one that cost $1000? Probably not, since I don't want to spend $1000 on a subwoofer (just a matter of priorities, not that I have anything against either $1000 subs or those who like them).
This is a great VALUE at $300. If you want a deeper/louder/better sub, you'll need to spend a LOT more.