Yo Rfprice,
It is easy enough to calculate, but why do you want to know? Are you going to try to do some welding with one?
The amp is rated at 400 watts per channel into a 4 ohm load. The power formula is:
P=I^2 x R (where: P=power in watts, I=current in amps, and R=resistance in ohms)
400 = I^2 x 4
(divide both sides by 4)
100 = I^2
(take the square root of both sides)
10 = I
(flip the values across the equal sign)
I = 10 amps
If you are driving 8 ohm speakers, then the current would be half of that or 5 amps.
The 400xi might have a little headroom, but not much.
Unlike its big FPB brothers, the 400xi doesn't like to drive low ohm speakers. A friend of mine hooked one up to a pair of Apogee Stages (3 ohms nominal) and the Krell got hot enough that it melted solder joints on the circuit board.