I brought my cab to the New England GTG today and tried a whole bunch of heads through it.
Verdicts:
1) TC RH450 - I really, really liked this pairing. Warm and middy, but plenty of punch and good low end without being too deep. Onboard compressor and adjustable grit really made it feel great.
2) Mesa Walkabout - Very clear and articulate, with easily adjustable EQ. Great little bit of growl with the gain pushed. Didn't have quite the "push" of the RH, but that was probably due to both the lower power rating and lack of onboard compression. Definitely #2 after the TC though.
3) Shuttle 9.0 - Not a great match. I'm not a huge fan of the Shuttle voicing anyways, but I felt like there was a lot of sound coming out, but nothing to "hear" if that makes sense. Lots of top and bottom but no mids or punch, even when boosting the mid EQ. Some of this was probably due to the room, but I don't think that this is the head for me.
4) Little Mark III - Good match. I prefer a little more EQ control, but the overall voicing was pleasant and punchy, if a little bland. Not quite as nice as the Walkabout, but no slouch either. I would gladly gig with this combo.