I can help you with getting the Theftlock unlocked if you replace it with an identical unit. If you go aftermarket, you don't need to worry about it. I just replaced the stock cassette head unit in mine with a CD head unit from a friend's wrecked Lumina. However, he did not know the code to unlock it (I didn't know the code for mine either) but I was able to pull some strings and call in a favor, and I now have the code unlock procedure (top secret!!) I think I've seen it posted here, too. Dealers charge $50 to unlock 'em. Bastards.
I do like the Delco/Bose units, they seem to have adequate power for my listening needs, and a useful control setup. Besides, I'd rather plug and play than mess with adapter harnesses and instructions. For $25 for the unit I put in, I'm very happy. I'm suprised my speakers aren't hammered yet, loud as I go with the kinda music I like. Seem like very good for stock systems.