Its really hard for me to play origional sins after the expansion packs... There are numerous AI improvements in the expansion, which makes regular sins seem like easy mode. you also generally need the expansions for the many mods. Id get everything, I saw a trinity on sale for 30$ at target the other day.
I'm not convinced that the AI is smarter in the expansions because it has no idea how to deal with starbases properly. Thus, it's possible that the AI in original Sins is smartest (because it won't be stupid about starbases). However, the Diplomacy expansion adds two new, nastier AI difficulty levels (which are really just eco-buffs) with Cruel and Vicious AI.
just, one thing with trinity, there are 2 files you have to delete, else if you hit up multiplayer youll get some wierd mesh files dont match error... and they are in a hidden folder.
It's not too hard to fix. Anyone who's reading this and needs to fix it can find a thread about it here:
Online Multiplayer Mesh Error Fix