Wow, that's unreal... I read through your post quick and kept waiting for an audible difference in tone, at first I was like where is the clip of the other setup? Wow.
So I have the Behringer Ultra-Di Di100, did I read and understand you correctly that you place this between the AMP out and the Speaker? Under that load? I had no idea you could do that! Before i blow up gear... do I understant you correctly?
So I'd being going out of my Orange TH30 head's 8ohm speaker out, into my DI and then into my cabinet? then of couse use the DI to capture the audio into my Presonus Firepod or M-audio FW410
If in understand that correctly, wow! That's pure tube tone! That's a game changer. I always felt that leaving through the effects loop robs you of your power amp tube goodness!
Plug into the DI100's balanced 1/4" TRS or XLR input, then send a signal to your console via the balanced XLR output. You can even plug your guitar or bass amp's speaker output into the DI100, which can handle ratings of up to 3,000 Watts and still deliver a perfect signal.