Don't let people who haven't tried, put you off.
I had a GH-6 for many years on my Moulton APB after finding it NOS (new old stock) in a bike shop.
I eventually became aware of the new LED lighting and upgraded to a SonDelux and an MK1 Edelux headlight.
I couldn't initially afford the wheel build due to wanting customs sized Sapim CX-Ray spokes so decided to see if my old Sturmey Archer GH-6 would make the Edelux at least flicker, knowing that it was reported that they were 1.8 watts.
The result was I almost didn't bother getting the wheel built up with the Son as the GH-6 lit up the Edelux just fine.
Was it full power?
I don't know but it was bright enough for me and was amazing after playing around with old lights for years.
I still have the Edelux but now use a Son dynohub.
Not because it might power the Edelux brighter but due to the GH-6's weight of around a kg.