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There is a FAQ in the FAQ section that I wrote a few years ago that helps determine alternator needs. Basically, you need to figure out the peak current draw of your amplifiers, or at least their typical draw at your listening levels, then add that to what your car needs to function (most modern stock alternators don't leave a lot of room between their rated output and the car's actual draw with a lot of power accessories and computers etc)

If you have a 105A, figure your car is using 70-100A, to be on the safe side, unless you have a clamp Ameter to measure the draw with everything running (HVAC, windows, etc)
then take the draw of the amps and add that to the total. use [i]HOT[/i] ratings, not Cold for the alternator.

I've done the big three upgrade with 0 gauge wire a couple months ago, but my stock alternator is 105amps and it just cannot pull the extra power so my interior and exterior lights dim significantly when the bass hits and voltage drops to 9-10. I'm in the market for a high output one as I figure that's the next step in solving this problem. I've looked on eBay and found a couple 220-250amp alternators anywhere from 150-175 which is how much im looking to spend. Will anything 200amps+ be sufficient? Anything i need to know further and will the amperage be enough to solve the problem? This is on a 2000 GMC Yukon Denali.

Thanks