The differences between the 4T and the 5T do not end at extension. I would wager that the 5T can get louder with less distortion and have a greater dynamic response. If you do get the 4T, you will need to crossover your sub at 120 hertz, which is pretty high, and now you have a issue with subwoofer localization. If you can deal with towers, I think the EMP might be a better value, to be honest.