well, im sure you know this but almost any medioker sub can get decent numbers if it is properly installed for the conditions, so the watts and number it hit in someone elses vehicle really dont tell you anything about wether or not you should buy it unless you plan on putting it in the same enclosure.
As to wether or not you shoudl get one, what do you want from a sub? Do you want one that can fart real well or one that can sing? Or possibly a farting singer?
What kind of power do you have?
What type of price range are you in?
What is your vehicle/plans for the install?