Can I use a di box or a microphone preamp while recording with a spider v

[bendagostino8]

Im thinking about buying a spider v combo amp mainly for practice but also for recording via USB. I currently use a focusrite Scarlett recording interface for everything but it sounds 10 times better with either my radial di box or my ART microphone preamp which has a specific setting for recording guitar. Would I be able to use a di box or mic preamp with the spider v combo? How would I connect it to the amp?

Also....

While recording with the amp as an interface does all of the sound from my computer come out of the amp or is it only the guitar sound?

Any help would be much appreciated 

Thanks