No I've not tried the Hi Brit, which is a True Brit with a Kapton voice coil, unless I'm very much mistaken.
The Retro 55 was designed by Paul at Tayden, and is not really the same at all as a Fane. I'm not sure where this info came from.
The Retro 55 has a 2" voice coil cf to 1 3/4" for most British-style speakers, eg G12H, Blue etc, and the larger 50 oz magnet.
The larger VC means their is a greater length of wire in the VC gap, so can generate more force, and also means higher power handling as there is greater thermal mass.
The 55W rating is very conservative for this speaker.