Which size subwoofer?

I'm currently in the process of researching the prices for how much it would cost to buy my friend a system. I was going to install it for her but was curious as to what would be the best size subwoofer to get. She wants to keep it as cheap as possible and low watts but still sound good. I've been leaning towards the JL Audio W0s because they are cheap, have low wattage, and JL Audio is a brand that I trust. She listens to hard rock and not rap so I was curious as to which subwoofer size you guys recommend. Thanks for any help.

My opinion is, 12s are the magic number. You get the best of both worlds, they can be hard hitting and get real low.

Agree on the 12's as they can do whatever you want them to. On a personal note, I listen to mainly rock/metal and my last system consisted of 2 JL W0 12's driven with 85 watts going to each and they hit really good. But, on my new system i went with 10's instead( not JL's) just to get a tighter response out of them and better mid-bass out of them. Plus the 10's i got hit just as low as the W0's did so i didnt lose anything that way. Either way it will sound good. Now i've always used ported enclosures as well, makes the bass drums really kick.

Yeah I agree with using a ported box since you were saying you wont be using much power.

either 10s or 12s would be good if it is setup well... what kind of money is she wanting to spend on this venture?

the jl's are a good choice. the jl plant is not far from me they make a good woofer even the wo is good even if it's entry level. i would go with 10's if shes a rocker. 12's will be fine as well.Big Dave

She is willing to spend around $200 dollars. I am going to build the box myself and install it all, need the experience. I will probably use the 10's since you all seem to recommend either both or just the 10s. I will probably go with a ported enclosure like someone recommended. Also, any decently priced amps that you recommend for this setup. Thanks for all the advice so far.

there is a port size calculator on this site make sure you follow the jl box size and port size for you to get the most from the tens. How much power are you going to play them with? Big Dave

Thinking about a 500 or 600 watt amp. Any specific amp though that you guys recommend? I downloaded the spec sheet for the subs so I have been looking at that. Thanks for all the great help you guys have given me.