Will the Infinity Basslink work under the front seat or should I get the Kenwood WooX? I am not looking for a hard hitting sub, just something that adds some decent bass. I also like the fact that they have a remote. My wife hates any kind of bass and it is her car. I would like to be able to add some bass without upsetting her. I also do not want a tube as cargo space is at a premium.

They look pretty high.... check out crutchfield.com for demension.

I had the same though... except I was thinking a custom box for a 10"

I considered the same thing until I saw a BassLink in person. I doubt it would fit under the seat.

How about something like this Clarion unit?
http://www.clarion.com/usa/product/index.php?mod=details&category=p_speakers&product=SRV303

It's more compact than the BassLink. Some people have installed them under sportscar seats, so there should be no problem with an xB.
Looks like it would be good if you're just trying to add a little bottom. If you want massive bass, then you probably wouldn't be happy.

I know that it wont fit if you stand it up, but I think you can mount it laying flat as well. I have heard that they are the best of the "mini" powered subs and found one for around $150

have you thought about building your own box? I'm just about done with mine and it really hasn't cost that much and is pretty easy to make(thanks to the knuckledragger at home depot for making those cuts). I too thought about getting a ready to install unit (the woox), but I was going to upgrade the speakers and would need an amp anyway. The wood was about $23 and have enough left over to make shelves/small cabinet/whatever, screws/glue $7, 10" RE sub $67 shipped and maybe $10-20 misc costs. Granted I had to buy an amp but you'll probably want to upgrade the other speakers later= new amp. Just something to consider.

btw- read good reviews about the woox considering its size but hard to find one to actually listen to. Seems like a good value if that's all you want.

Even if you lay the basslink on its side its still to tall, I would say unless you can fit a volleyball under your seat (pumped of course *hehe*), if you can't then no way the basslink will fit.

Basslink dimensions according to Infinity: 14-1/2" x 12-1/2" x 8"

So make a cardboard box that size and see if it fits.