imo the 1508's are the best out of the 1500 series. if you want to stick to the 1500's then id go for the 1508's.
if you want to do 10's then i would go with the 2510's all day long. the 2510 is 10X the sub compaired to the 1510 imo.
i ran a 2510 on a mtx 81000d for a few months in my s-10 and it was quite impressive and took the power great. i even ran it in the wifes car on a 6500d and it did very well on 500rms as well.
i currently have a 1508 in her car with the 81000d and that little son of a ***** gets it good for an 8"
with all that, if you want the 1500 series, go with 1508's
if you want 10"ers, go with the 2510's and be done with it.