I know this thread is old, but there isn't much info on the PF15TL and PF15TL+ on the internets, so anyone looking to buy one of these vintage models will probably end up here. I felt that many of the comments here were misleading and not entirely accurate, so I'm going to share my view.
Depending on what you're looking for, the PF15TL+ can be a very good choice, rivalling some of the best subs even today. I've owned a PF15TL for 13 years, and recently the amp died. Based on the not-so-glowing reviews on this forum I decided to purchase a new sub instead of repairing the 15TL. I purchased the Epik Legend 12" subwoofer which is generally agreed as one of the top 3 subwoofers at less than $600. Upon setting it up, I discovered that it is, overall, barely superior to the PF15TL. The Epik has much better reproduction of higher, snappier bass, while the PF15TL is better at the lows (<50 Hz) or so. Let me say that again: The 13-year old PF15TL reproduces deep bass better than the one of the top rated brand new subs today! The PFTL bass reproduction falls off quickly at higher than 50 Hz, however, so it isn't very balanced for most music. Basically, if your main purpose is home theatre or hip hop music, go with the PF15TL. If you want balanced bass reproduction and the ability to hit the middle/upper snappy bass, the PF15TL isn't a very good choice.