So basically i d.i. my guitars as well as having an sm 57 recording through the cab. I use to use a tube screamer to tighten the sound but now i've cut it out. Me and my mate were having a conversation that neither of us knew the answer to.

Can you stick a d.i. box between a head an cab?
Further more, can you run a d.i. box through your effects loop built into your amp?

Mine use to go between the end of my pedal chain and before the amp. Being aware of ohmn's differences and all that we both thought no but neither of us are 100% on it.