Originally Posted by C-bro
Agreed. A decent quality 12" or a pair of 10" in a sealed enclosure will give you tight, responsive bass. I know almost nothing about techno/trance but it's my understanding that there are a lot of fast precise beats. With something larger than 12 or something in a ported enclosure you run the risk of the beats becoming "muddied" into a sort of single rumble. Now of course there are always exceptions, but as a rule of thumb sealed + 10/12 will deliver an excellent bang for your buck. Just be sure to match your drivers to the proper enclosure size (or better yet build your own).
As far as brands I think pretty well everyone has mentioned the decent buys and the ones to stay away from.
I'd agree. If you haven't heard a good system before, 10" subs are good for hard, quick bass and are (usually) very responsive. 15" subs are good for low, long bass. 12" subs are a good sacrifice between the two - I think trance has some of each type of bass, but mostly hard-hitting.
A good 10"/12" sub, an appropriate box, and the right amount of power can make the bass feel like someone is punching you in the chest.
The kicker (no pun intended) is going to be finding what you want to buy - there are so many car audio parts/brands/components out there at so many different price points. Personally, I like to go with old and new. I'm a huge Orion and Rockford Fosgate fan (the old stuff, not the new), so when I went to build my first system in high school, I went used for the amp and subwoofer. I've since sold the system and am currently going without subs. I bought an old MTX Blue Thunder Pro amp for my mids/highs about 3 years ago, and it has served me well ever since.
These are the two components I had in high school:
Rockford 400x4 (when their amps rocked)...
Orion XTR sub...
I miss them! I shouldn't have sold them!!!!
EDIT: These aren't my pics, I don't have any pics of them in my Chevy Celebrity when I was in high school. Sorry.