Which air can for Heckler?

This should be quite simple, but.........
I'm looking at either a Fox Float in RP2 or RP23 or RockShox Monarch in 3.3 or 4.2. I've found a couple of cracking deals on pretty much all of them, but I'm drowning in options!
I've got a '06 Heckler and getting steadily more and more confused about standard or high volume air cans, and the compression tune? Please help, I'd rather get the right shock to start with and not be thinking about further tuning for a while yet.

Going to x-post this in the Santa Cruz forum too.
Thanks in advance.
Pete.