Here's an answer in advance to many questions that I've seen popping up around TSS.
I found this great chart on Tama Zone
that shows connection compatibility with all the Connections up until the Uratama.
Check it out here
I find it very very useful, and I'm sure everyone here will get use out of it too! I ordered an extra Entama, Uratama and Akai off eBay last night on the basis of the information on that chart.
It shows not only whether or not any two models can connect, but also whether or not they can mate. It's not always the same!
Hope everyone finds this handy!