Don't see the point in investing in a large subwoofer if you're just going to reduce the bass output.
If you're after low/mid frequency output with alot of punch, stick with the 6 x 9 or 8 inch speakers. Going larger than this is unnecessary, you're really just paying more for traits you don't intend on using. Punk is very much about speed, punch and treble. Bass plays a very small role in this genre of music. Setting up a sound system to produce alot of bass will totally ruin the core aspect of the genre.
I wouldn't buy a V8 if I was after fuel economy, and I wouldn't buy a 12 inch subwoofer if I was after higher frequency punch without sustained bass. Bigger isn't always better, choose to suit.
I think alot of people are missing this philosophy in their audio setup approach these days. Sound quality is more than just massive bass output, there has to be balance. Getting a 12, 15 or 18 inch subwoofer just because you can is ridiculous, if it doesn't suit the music you listen to, or you're just going to turn it down, then you're only making yourself look like a fool with too much money and no sense. I find that larger subwoofers are not responsive enough to keep up with the ridiculous speed that alot of punk bands play at. The bass becomes smothering and it loses all definition. Stick with the mid/high frequencies and you'll find the music sounds alot better.
Sorry for the long-winded opinion, hope you all don't mind the ranting.