I don't know how low you want to go, but the 10 fares really well. It all worked out because the 6.5 inch speakers were also replaced, and the sound deadening/insulation made for very atmospheric sound.
sound deadening is more than i want to do right now. I like the p300-10 but thought if i got a 12 inch shallow enclosure that is something i could keep and never feel was inadequate for years to come. I got the p300-10 for 173, that pioneer enclosed 12 is 129 + 10 for high low converter + another 70 or so for a whatever amp. I'm kind of thinking out loud here as I am still new to all of this. I think it kind of feels like I have more of a really good stock sub than something that I added to the car. Maybe those components later will help.
EDIT: if i just keep my p300-10 and install components up front like polk audio dxi6501s can i tap into the built in amp in the p300-10 or do i need to get a separate amp?