I have paired my Hegel H30 with a VAC preamp and now a Luxman 600 preamp I picked up here on audiogon. I prefer the Luxman preamp with the H30, but miss the built in phono stage in the VAC. The Luxman just seems to work really well as a good sonic pairing.
The Hegel H30 is a terrific amp. It has a 3D/holographic type sound compared to many similarly priced AB amps.
I too have tested H30's in mono and as Robert Harley (TAS) found, one (stereo) is better than two (mono).
As a side, there seems to be a consensus among people I spoke with that the Hegel P30 preamp is not quite up to the level of the amp. Most people suggested I find a different preamp, but I never tested the P30 in my own system - so I can't be 100% sure.
YMMV.
Mike