Best amplified subwoofer for your money?

[NSSS]

I'm looking for a subwoofer to compliment my system, tight with space. Right now I have a pair of pro80's with 4 Polk 651mm in the boat. Looking for something that will be decent to go along with this stuff. I've been looking at all the bazooka tubes but don't have any experience with them. They seem to have a lot of options  ranging in size and rms wattage. Also there are a lot of other companies making amplified subs I'm open to, but then again I got no experience with them. I'm on a budget going to school right now, don't really wanna pay more than $250 but if it's worth it I'm willing to go higher. I'm from Canada, the Canadian dollar killing me right now! Just want some insight on what you guys think. 

[That Guy]

I installed the Infinity Basslink under my drivers dash. I bought it used for like $75 but they are new under $200 and it is everything I was looking for l, and more. Now I'm not an audio nut but it added significant bass/lowend sound to my boat. It vibrates the floor/hull when it hits hard, which again is more than I need so I've turned it down some. I'm sure some won't be impressed but for my needs it's great, and everyone I've had on my boat has complimented me on it. 

[Michigan boarder]

8 minutes ago, That Guy said:

I installed the Infinity Basslink under my drivers dash. I bought it used for like $75 but they are new under $200 and it is everything I was looking for l, and more. Now I'm not an audio nut but it added significant bass/lowend sound to my boat. It vibrates the floor/hull when it hits hard, which again is more than I need so I've turned it down some. I'm sure some won't be impressed but for my needs it's great, and everyone I've had on my boat has complimented me on it. 

I have the same thing, in the same location, and it performs the same way.  I bought mine used, $100 shipped to me from a guy on this site.  It's been perfect.