Ah good old tekkit. Now there is test pack please ignore which shows promise but to be honest the modding scene slowed down after the bukkit/forge mess and due to the fatigue of never receiving the promised stable api.

The moment ic2 stopped development I lost interest.

Buildcraft spawned factorio however, so my logistic nerd needs are satisfyed :)

IC2 never stopped development, it just became... different.

I haven't but will now

I recommend you start with a modpack.

That said, not just any pack will do. My absolute favorite is TPPI2; I think it's by far the most professional one, but it does require a pretty hefty machine. If it doesn't work, then there are a number of smaller/more specialized packs that likely would.