I have a 15" "classic woofer" too and, for the money, you can't go wrong. Only downside is a fairly high Vas which will tend to put you in a larger cabinet, or sacrifice a few db in the lower frequencies. The classic sub is a very nice speaker too, 4 ohms might be better for a car and a Vas of 9.7 vs 14 will mean that you can get about the same performance out of a box 1/2 the size.
For subs, I am currently running a classic woofer on one side and a Series II on the other, both in 5 cubic foot ported boxes tuned to 25 hz. The Series II is better, but the classic woofer holds its own and they seem to mix well together. I'm running them in parallel, so I needed 8 ohm speakers as my sub amp is only good down to 4 ohms.
Dan