I can offer my input on the PV1.
I had a Sunfire HRS-10, paired with B&W 684/686/HTM62 and Yamaha RX-V1900 and 'upgraded' the sub to the PV1.
The difference I hear from movies is a tighter, more accurate, short punch, compared to soggy, flabby long bass I got from the HRS-10, which is a £1K sub - same price as a PV1 roughly. In addition, the bass from the Sunfire tended to sound one-dimensional with every bass note sounding the same with no variance. The PV1 tends to sound less 'coloured' you could say.
For music the PV1 is better too. It seems to keep up with the musical basslines better than the HRS-10, which always felt kinda retracted a little. The PV1 also amazes me how you do not get any cabinet reasonance or rattle - only the drivers move.
People say that other subs can go lower than the PV1 for half the cost, but I personally don't think that its the defacto for a large percentage of us that use our systems in your average sized rooms. Plus it looks great!
Now I haven't got a problem with spending a grand on a sub. I don't want a great big massive box or cylinder in my room for the same money. You could view the two splendid 8" drivers as one large 16" driver for those that bang on about 12" subs. Cheating, I know!
I hope my feedback has been helpful.
Samsung LE40F71BX | Yamaha RX-V1900 | Pioneer BDP LX52 | B&W 684/HTM62/686 | B&W PV1 | V+ | PS3 | Xbox 360 Elite | van den Hul Flat | Chord SuperScreen