Replying to Hey math wizzes (graphing calculator question)

I am in a pre-calculus trig class this semester and will most likely be taking calc 1 and 2 before I am done with school. My teacher suggests I purchase a Ti-82,83,85, or 86 graphing calculator. The 89 and 92 isn't an option. I am going to buy this off of Ebay tonight so emailing him wont really be an option. I would have started looking sooner but I just got done with a 5 day shred and destroy road trip and have not had internet. Do most of these calculators do pretty much the same thing or are there noticable advantages to the different models?

I've done a little research and I know some of them have flash memory cards and others have USB connectivity. I couldnt find any info on the 82. Anyone have advice?