SLI/Crossfire Question (noobish)

Okay,am in the market for an 1156 board at the moment; and am looking to crossfire/sli later on for some extra performance.

Now, to my understanding...Crossfire works on all boards with two pci-e slots? Most of the 1156 boards have this listed anyway.

I would like the option of going either way however...and I can't seem to find any mid-range boards that list SLI compatibility.

Is it the same kind of process? being that as long as you have 2 slots you can use SLI?

(I read through the stickied FAQ and couldn't find an answer   )