The SVS PB-10 at $429, won't work for you then, because it does not have a crossover. From them, you'd need to step up to the 25-31PCi cylinder or PB-12, which are $500 and $550 respectively, IIRC. I've owned the PB-10 and it is a great sub for the price.
There's also this guy:
D12. I recommended it to my buddy and I got to put it through its paces this weekend. Not bad. It doesn't seem to go as low as the PB-10, but it does a respectable job and it's tiny for the output it is capable of.