The Hiwatt sound is Clean like a great Blackface fender, with less coloration, but punchy and aggressive like a Marshall.  It however is more dynamic due to its cleaner sound (higher sensitivity).  Think of playing ACDC totally clean and really enjoying it!

The Ceriatone Heywhat is more like an original Hiwatt of the late 60s/early 70s where as a 'Hiwatt brand Hiwatt' is not what it used to be.  The real choices are a Ceriatone or a Reeves.  The dude doing the demo on the NEW Hiwatt above video has a pedal in front of that amp he isn't showing u, a Hiwatt does not have that much gain.  The 1972 demo is very close to the Heywhat, its the best online demo I could find while researching this amp.

I have the Ceriatone 504 version (50watt) and it easily keeps up in clean volume with my Marshall JTM45 blasting its face off thru a 4x12.  The 103 is only 3db louder, which just barely enough to notice.

IMPORTANT: This amp does not work well thru just any speaker type.  Nasty, bright sounds thru Celestion GH30s, Greenbacks, V30s, not that I was expecting these to work.  I went with 4 Webers: Fane Crescendo speakers.  It sounds amazing.  Clean is great and can handle a medium amount of breakup.  Pink floyd to the Who, you got it.  Old Fanes are hard to come by, save yourself the trouble and go with some Webers.  The Cresendo was specifially recommended to me by my cabinet builder instead of the other Fane reissues by Weber such as the 'Thames' or 'Axis'.  The Axis handles more gain, and the Thames is less sensitive than the Crescendo.  The Crescendo is the Middle ground and best for cleans, medium gain. After all, you don't really want a Hiwatt for lots of gain anyway.  Having said this I can get all the 'WHO' vibe out of mine I could have asked for.

I have heard a lot of great things about Reeves, but there is nothing I could imagine changing about the Heywhat 504 I got from Nik.  I got a half power swtich as well, it allows the preamp to be driven a little harder, great for more gain.  The channels sound great slaved, but it is not neccessary like on a 4 input Marshall.  AMAZING VALUE, Nik you are the MAN!!!