I am running two JL 10 inchers in my VX right now. Like KBoogie, I have been in the car audio game since the late 80's. I have run all types of configurations and sizes, 15, 12, 15 and 12, 12 and 10, band-pass, ported, sealed, even isobaric and the one thing that I have found is that as long as you build the box "right" (i.e. solid, well sealed where it is supposed to be sealed, and pay attention to ACTUAL internal volume of the box taking into account all of your bracing and the speaker frame and magnet itself) you will end up with a good sounding box. ALWAYS get more power than you think you need in your sub amp. This keeps you from clipping and keeps your bass sounding right. Run a proper sized capacitor with the right guage wire as well and you will be ensured of nice lows. It is important to be able to move large amounts of current and have large amounts on tap to ensure clean sound.

So what is the short version answer? On a budget you can make 2 10s sound right if you pay attention to what you do, EVERY ELEMENT of what you do. This means no weak links. Of course yours won't sound like the JL van, but you won't be spending tens of thousands of dollars either...