I could well imagine that power block doesn't sounds all hallelujah with drives in front. odds are that when u use modeling into its line input....you will get much better results. at venues I have used returns with a modeler of amps that were horrible using the front, yet when speaker and power section are half decent...with actually very good results.I understand this...I think.
I'm trying to put (and/or buy) as few components as possible. I actually own a Crate Powerblock SS. It sounds great clean, but useable OD tones have escaped me using it with pedals.
I have played through an Atomic CLR cab with an Axe Fx 2 and it sounded great.
I have the Axe Fx effects without cab or amp emulation in the FX8. I could try the Crate Powerblock with it through a Bogner Cube 112 I have.
Using this rig, I wouldn't have to buy anything new. The Iridium does sound great on YT, better than the Crate Powerblock at any rate...and I could go with that into the CLR...if I can find one.
Will get back.
To get an indication of what the result would be, if you own a daw, download the trial of sgear, switch cabs off and feed that into your crate + cab. Or if your tube amp has a loop, hijack the preamp at the send, and feed that into its line in. This way you can hear what it does with a good preamp in front of it, to possibly pair it with a modeler later. (don't be afraid to use a global eq when needed)
the iridium sounds great, but....if you want to use gain sounds + time effects, there is no way to split your signal into cabsimmed + non cabsimmed signal......so that would be " all in" on full range system. (or mic your cab)