The latency of Axe II direct with Fireface out will be higher than Axe II direct only...simply because the DAW software is involved. You can minimize that with buffer settings and such, but it will still be higher latency than recording and monitoring direct with the Axe II.
I don't know the FF800, but if you can use "direct monitoring" with the SPDIF, bypassing the in and out of the DAW, then there will be no delay. With the Axe USB, then you must go:
Axe II >USB>computer>Fireface 800>your monitor speakers. There will be latency any time you have to go in and out of the computer.