$200-$300 left over after purchasing the Axe FX II and monitors would be enough to purchase an interface. Unless I'm missing something, you'd have enough to make it work. Since you don't play out, you can always purchase a foot controller later, and you can always downgrade if you decide it's overkill. However, upgrading to an Axe II from the AX8 might take a bit longer once you've spent the extra cash should you decide you need the extra features and more power.
I wouldn't need an interface with the Axe Fx since its built in.