Actually you can. SVS offers a 45 day risk free trial period, full refund, shipping paid both ways, no questions asked. You could order 1 of every sub they make, try them all out and keep only the one you like. Now, that's an extreme example, but we had a guy who did order 2 or 3 different models and did just that. Kept the one he liked best.
Now, to make things a little bit easier on you, I'd forget about any sealed designs. Ported is always the better choice unless restricted by space limitations. To make things even a little easier I think the VTF-3 MK5 is the best bang for buck of your choices. I own a pair of them and they're legit. Clean, powerful and linear. Great performance for the money.