clio dynamique, you have alot of options open to you!
But firstly, dont pay attention to the certificate figure that you have, coz that is the first time it was started up & will never get that figure again, just ask your ice shops about that.
& about choice of subs.... You listen to trance right? (So do I) however I do listen to music at other times to so I got a 12", & I reckon you should get that too, coz everyones music tastes change at one time. & a good 12 can handle all types of music, I find that 15s are too big in my experience & only good for music that has long bass notes such as rap & hip hop & not much else.
I would recommend either Directed Audio or JL for a decent sub! Directed audio do the studio series, & their duel voice coil one for £150 rocks to sh*t which is better than the equivelent one by JL (the 12w3v2 D2)
But if youve got up to £300 to spend, then you can go one up from the studio series & get a Comp X! & these things are LOUD, if anyone went to the FCS, the blue 106 ICE car that was there had all Directed Comp X subs!
If your gonna go for a JL, then save up a bit more and get the W6, coz that sub rocks to sh*t
(im getting it next!)
Oh yeah, It will depend alot on what your head unit youve got & the monoblock/amp you have got.