I haven't been in the car audio circuit for quite some time. I had reaaally thumpin' bass. from 100 ft away, I rattled things in my friend's house's kitchen. I have heard many of the subs people have suggested, rockford fosgate, kicker, jl audo, jbl. I think that these subs are OK (JL audio pretty good), but I put in some sound stream SPLs, hell, I can't remember why, I just did it. I had a precision power A1200.2 (1200 watt RMS) to the pair of SPL 12s. OK, so the subs were rated at 300 watts peak. I blew one of them out. I got it warrantied from the place I mail ordered them from. But, to the point, I adjusted the gains a bit, and these pair of Soundstrem SPL 12s in a 1.5 cubic foot box(gross volume) with no bracing, no poly fill, no crossbraces and sealed with hot glue (not the greatest) completely rocked my world. I previously had 4 boston acoustic 10 inches in a sealed box with .7 cubic feet each. The bass coming from the pair of SPL 12s was much deeper, faaar cleaner, faaar tighter and a bunch louder than what I had. I know for a fact that SPL series subs have been around for a while, and I"m not quite sure what's out there these days. These are absolutely Great subs for the money. I've seen them online currently for around $120 each. These aren't built for heavy duty competition, but, they do handle a lot of power. Also, they are very forgiving on the enclosure and very versatile. They require hardly any space either which is a good thing. If the SPL 170s (15inchers) are _anything_ like the littler, less expensive SPL 10s,12s,15s, they will absolutely frickin' rock. I've been dying to try them, but I'm short on cash flow. I'm not sure about the Audiobahns really. Stats say a lot, so do the Theile small parameters, but hearing is believing. Honestly, I glanced over the SPL series subs many a time because their stats, like magnet weight and power handling are not impressive at all. Best way is to find someone with the subs your looking for with a proper enclosure., or find someone who is absolutely nuts about a certain type of sub. I'm in love with the soundstream SPL series and will be until I can find a better sub, for the same money or cheaper or reasonably more.
I recently built enclosures for a pair of Hifonics 15" generation x series subwoofers. I built one at 2 cubic foot each, an honest mistake on my part. The bass was OK, not exceptionally tight, pretty deep, but they started to distort at any increased power levels. That's understandable. I built another box. This box is perfect and made it as close to spec as possible. I made sure it was completely sealed, had braces, the whole nine yards. Basically, they bottomed out and started clipping without that much power applied to them. They sounded loud outside of the car, but sounded like crap inside. I couldn't believe that these things go for around 250 each. Am I doing something wrong? Gotta make a ported box for these? (****, can't stand the sound of a ported sub, so boomy and generally not as tight) But anyway, my sealed enclosure experiences with the Hifonics generation x15 subs have been less than impressive.
installation can be a total pain in the butt if you don't have the right tools and you haven't done it before. Mainly the big problem for you I'd guess is getting the amp installed. That's not that expensive to do really, maybe 50-60 for the install job + materials. Finding someone to do the box custom can be difficult to do, and can be costly. When you're going for mad bass, it's almost necessary to build an enclosure that is specific to your car, or you'll end up wasting too much trunk space and almost always causing you to lose SPL and sound quality. I happen to have a complete woodworking shop and have made many a box in my day, probably 20 of them for myself, just to try out different types of enclosures -- isobaric, bandpass, ported, sealed, big ports, little ports, braces, cross braces, no braces, completely sealed, leaky, varying volumes -- you name it, I've tried it. I'd be willing to build a box for you custom for a very reasonable price. Hell, I love making them. It costs like 12 dollars for the wood, 10-20 for speaker terminals + extra for extras like exterior finishing such as carpet or formica or a solid sheet of plexiglass or mirrors or neon tubes of light if you wanted to get really fancy, and of course, labor costs. Well, hope I've been informative for y'all.