Thanks for the info. That looks like it will be the route I take. I was looking around on eBay, and found a guy selling factory refurbished MTX equipment with MTX warranties, and it looks like I could get a Thunder 311D amp (100W RMS @ 4ohms), and a Thunder 8000 series 10" sub (which I assume is last year's model, since it's not on MTX's website) for under $200 shipped. Will this work well enough?

The other thing I noticed was that you've got component speakers in your car. Would these be worth the upgrade in a 3-speaker system, especially if I mounted the tweeter someplace up high, like the A-pillar? My dad, who builds hi-fi home stereos for a living, said that that would probably help the higher frequencies...

Oh, and I forgot to ask this earlier, do I need an antenna adapter for my new HU? I seem to remember reading somewhere that I do....

 

100W for a sub is pretty weak for a car stereo system. I would recommed "at least" 250W (preferrably more) for a single subwoofer installation. I don't have any experience with MTX subwoofers myself.

Yes, components are worth it IMO. I am not a fan of mounting tweeters up high. I prefer a "point source" style of speaker mounting where all of the frequencies are coming from the same point in space. Not spread out all over your door panel.

Yes, you need an antenna adapter on all GM cars if you are using the stock antenna.