Well as the title says, I have a 2004 LX 5 speed. I am pretty content with the stereo other than it seems a bit underpowered (IE gotta turn it up "high" to hear a "normal" level of sound) and I like the sound overall but the low bass is lacking.

I was looking to get a single 10" subwoofer in my trunk with an amp, hopefully installing it with a Line Output converter.

I see this style enclosure:

http://www.mainstreet-audio.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=QL-C1HCV110

That's what I would like to get, but $200??? There has to be one that isn't so expensive.

Any advice for wiring it up and getting a decent enclosure let me know, thanks much!

It doesn't really look like it fits perfectly like a custome enclousure should. Personally, I would spend money on that one in particular. What subwoofer are you looking at?
A custom build box by YOU would probably work better. Just be sure to keep to the specifications/dimensions provided by the subwoofer booklet when you buy a sub. Some people build it into the spare wheel compartment, some just build a basic rectangle box.
Basically, just consider all your options before you dish out $200 for something that doesn't even look like it fits that well.

Thanks for the reply! I was not planning on buying that one, it was just to give you an idea of what I'd like to do. I'm not that much of a craftsman and would rather buy one made, and also time is a factor I have enough projects going on.

I have no idea what kind of sub either. I'm just looking to get some nice smooth low bass added to my sound. It doesn't have to be one that shakes the neighborhood though.

A 10 in a prefab MDF enclosure will work better than that Q thing. tackie lookin. That "spot" in the trunk is a good place to locate the sub..... but.
200 bucks won't get you a lot, so be aware..... don't buy junk.

maybe try something like mine?

http://pic20.picturetrail.com/VOL171/6832453/13120238/251599289.jpg