I think you're right; I hope you're right! It's less weight, less money and I think, should sit at about the power I'm looking for! I'm going to go for exactly what you've listed here. I'd already decided on that sub and I already have the Pioneer components, but the power pack I have to admit I'm dubious about, though generally it's well reviewed. A good choice to replace the FLI's I think, probably better to have slightly more amp power than the speaker needs from what I've read and frankly, I'm sure the pioneers are simply better than the FLI ones in there anyway. On top of the kit though, I am going to make frugal use of some sound deadening/anti vibration stuff (along with blue tac!) to help de-rattle the car a bit/make the most of what's there.
I guess we'll see how it pans out when the time comes and it's all in and fitted!
Thanks for the advice/help in decision making!