[quote name='TimTucker']I believe the 86 can also be used on the SAT/ACT (at least it could be when I took it when the 86 was actually new).
I'd say that which to recommend varies based on what you're going to do with it.
If you're going to be doing a lot of things for calculus & beyond (i.e.: calculus based physics and statistics classes, etc.), then the 89 is probably your best choice.
If you're going to stop at initial calculus stuff, then the 86 might be the better one to get.
From having used the 86 extensively and having tried the 89 on a number of occasions (and having known quite a few people with both), I'd say that it's much easier to do things quickly on the 86.
However, if you have a lot of use for the 10-15% or so of functionality that the 86 doesn't have (like symbolic integration), then you'll need the 89.
If it were me, I wouldn't even be thinking about the 83. (the menu systems are much more cumbersome than those on the 86 -- after a few years using the 82, which uses the same menuing system as the 83, I would never want to go back)[/QUOTE]
The reason I recommend the TI-84 Plus is that the TI-86 is no longer manufactured by Texas Instruments. They also made the TI-84 Plus with a Silver Edition right off the bat. The built in clock is a great feature as well for test taking and class sitting. All of the high school math classes I took, the teacher used a TI-83 Plus for demonstrations, and we had TI-83 Pluses for use on all of our tests. The 89 is NOT allowed on the SAT/ACT.
OP, I recommend spending some time on TI's website at:
http://education.ti.com/us/product/main.html to find out what calculator best fits your needs. Then watch store flyers for deals. I have found that the best deals are usually found in the fall around August or September when the school year is beginning.
-Jeff