It'd help if you said what kinda car you have (Speaker sizes, ) but oh well. Here goes.
You'll want to have more than just bass, you'll need some speakers. I recommend some 6x9's
http://www.crutchfield.com/S-nb7JX4R...&avf=N&search= 59.99 (+ shipping... ?)
You'll also want a damn Cd player, or Head Unit. Heres a Kenwood KDc 222 or some #, But i've got one JUST like it and it works just fine, for not too much money. They've got it listed at
99.00 + shipping (?)
http://www.crutchfield.com/S-nb7JX4R...300#morephotos
For some bass you'll need some 10's, 12's, or 15's. I recommend 12" subs, they are great for in your car (Like 10's) and you can hear them from a distance (like 15's). But here are some Kicker 12" Comps,
http://www.crutchfield.com/S-nb7JX4R...&avf=N&search= You actually get two of em for
$128 (+ shipping)... which Isn't too bad.
You'll need a box to put your Subs in, here is a dual 12" Q-Logic box for
134.99 (+Shipping)
http://www.crutchfield.com/S-nb7JX4R...&avf=N&search=
Now, you'll be wanting to get it installed, your going to need some RCA cables, wire for power, the remote, and some ground wire, you can usually get all of this crap in a kit from any audio supply place for about $
20 bucks.
So far, you've only spent $440. You still need an amp for your subwoofers, so for your price range (in this scenario) your going to have to get something smaller. Here is a Kenwood 40 x 2 watt RMS Amplifier, it's
89.99. Your speakers are 25-150 watts RMS, so you'll be fine.
The total comes to (WITHOUT SHIPPING): $529
What i'd do is shop around, find out if any speakers/sub systems are especially made for your car. What you can do is go to
www.crutchfield.com and they'll tell you what you need for your car, and how much they offer it for. (But if you would have shopped around, and not bought it from Crutchfield, like I just did your system, you will probably save around $100)