mgm controllers.....TMM?

[tashpop]

i found a little write up on the mgm controllers and found out there are two types, SMM and TMM oh, and also TMM extra. from the reading, it looks like any of the TMM controllers could serve as car duty controllers as long as amps and voltage is matched up. i know there are some controllers without the heat sink, and it looks like that is the only difference. am i right in my thinking? i'm just trying to know all options before i make the plunge in my purchase.