<p>You should get a TI-83+. The [signing</a> key has been cracked](<a href=“http://www.ticalc.org/archives/news/articles/14/145/145154.html]signing”>TI-83 Plus OS Signing Key Cracked - ticalc.org), so soon enough it will be possible to run all manner of software on the 83, including the CAS from the 89 & the Nspire.</p>