JBL PB12 vs. Yamaha YST-SW315 Subwooofers  

I have a $100 PB12 that I could get a new amp for $128 and make it a $228 250w sub, or get a Yamaha YST-SW315 for $189 plus $40 shipping to make it a $229 sub. Basically the same price in the end. I'm torn between the two! I love Yamaha, have 2 HT with Yamaha speakers and recievers (only one Yamaha sub though...55watts too in the family room). I want to keep the JBL just because I don't want to have to return the big thing because I bought it from across the city...but I'm worried about not using the original parts for it and just buying a 250w amp from partsexpress.com, like I don't want to have to refit the cutout in the back and worry about something breaking on it later. What's your thoughts and what would you do?

Tim

Somebody has to have know what they're talking about when it comes to putting different amps on subs. Do you have to modify the box at all??? That's my real question...