I would hit up a junk yard and get an alt off a full size. They are called an AD24 and are very common. If you get one off a fully loaded Tahoe or similar it will be around 190-210amp. You can snag it from a junk yard for about $40 or so. You will need a little longer belt in most cases .25- .5 inches longer then stock. Other then that it is a direct replacement.
If that is not enough power, then have a local alt shop built it up for you. Most will build it to a 250-300amp alt for a few hundred or so and that is by far the cheapest solution you will find.
We have brand new ones that can boost any sound system. Check out Mechman Alternators on ebay. We are offering a 340 amp model with external regulator for $549. That's about $200 less than our normal price. For something less gucci, we do offer a 200 amp for $399. All of our alts come with a 2 year free parts and labor warranty, and then an additional 10 years free service if it ever gives you a problem. Hit me up if you are interested. Have a great day!