Boston pro 12.5LF or Fusion FPW1000?
 

Not sure what to go with for a sub.It will be used in a reg cab s10 and run off a zapco studio 500.I'm on a budget and was hopeing to have just the one sub.I;m looking more for SQ but would also like the SPL.

I have zero experience with the Fusion model so I cannot comment on it but I do with the BA 12.5LF so....
Although it is a beautiful sounding SQ driver that can stay accurate and play a nice bandwidth with authority even in a small 1.0net sealed enclosure it may not be what you are looking for if you're expecting it to really wang also.

How much airspace do you have available to use in that S10?

Resonant Engineering SE, Image Dynamics IDMAX, OZ Matrix Elite, JL W6v2 would all work well in smaller enclosure's either sealed or ported and with the power you intend to use. All of which are quite deep in terms of installation depth though.