I've got a few questions, the first one is can I run a sub off my stock system? Its not the 460, just the plain base stereo for 98's. If I can, without having to buy a new headunit and stuff, what is the best size? I'm not looking for earth shattering bass, I just want something I can feel when I turn it up. Would 1x10, 2x10, 1x12, 2x12, etc be the best choice? I'd like to have some trunk room, so I was thinking maybe a 1 woofer setup, but will I still get good bass with just one woofer?

I'd be building the box and installing it myself, so what would you guys recommend? I'd prefer to keep it under 200 bucks for the whole thing, but that shouldn't be hard since I'll install and build myself.

 

Yes, you can run a sub off your stock system.

You will need a line converter to connect RCA wires to your amplifier.
http://www.amazon.com/Tsunami-Line-O.../dp/B00032CK8U
This takes your factory speaker wire and converts in to RCA friendly signals. Or, you might be able to find an amp that accepts speaker wires from factory (line-input connector).

I think 1 10" sub would be fine for you. Like you say, your not looking for earth shattering bass. I have 1 10" sub in my 97 convertible, more bass than I really need - even in a convertible. It balances out the system nicely.

As far as building box yourself, unless things have changed, use 3/4" MDF. Its like particle board, but better. Forget how much a 4x8 sheet at a hardware store costs, but its not expensive. You can also purchase carpet to cover the box, or think of any other ways to cover the exposed wood. I like carpet because its durable in the trunk and usually matches the carpet in the trunk.

Oh, and one last note, something to consider - not sure how "popular" they are anymore, but to conserve space, you can install a bass tube. Some of these come with amps already built in. They have the amp, sub, and enclosure all in one. Kinda neat. I know plye isnt the best brand, but this give you an idea.
http://www.pyleaudio.com/itemdetail....;model=PLTA10N

 

I would go with a ported ten or two of these ported

http://www.edesignaudio.com/edv2/pro...products_id=33

 

This will be a great setup for under $200.

Sub: http://www.edesignaudio.com/edv2/pro...products_id=31$100 (Dual 4 ohm and I like the black cone)

Amp: http://ikesound.com/product-product_id/2840$70

Wiring: http://ikesound.com/product-product_id/3367$10

An that leaves you around $20 for box construction.

Awesome setup!