Experience with Tannoy Westminster Royal Gold Reference

hddg -
For what it's worth I own a pair of Tannoy GRF Professionals, these have a back loaded horn similar to the Westminsters but with a much longer horn. The GRF Professional Speakers are physically about the same size as the Westminsters. I have heard many amps on these speakers and prefer by far very high high quality solid state amplifiers rather than tubes. I first head them with a heavily modified Perreaux 5150B, 500wpc, and the improvement in timing, particularly on large scale orchestral music with the headroom provided by this amp, is audibly superior to many high quality tube amps auditioned over the years. Tube preamp/solid state power amps are my preferred combo.

hddg,
I currently use a modified Marantz 7 tube preamp with Brown Electronic Labs power amp built by Richard Brown. Unfortunately Richard Brown has passed away and no circuit diagrams exist, so I would recommend trying some more current amps. The only thing you have to watch is that the power amp has a high input impedance relative to your Coincident tube preamp to ensure you get no bass rolloff issues. I would not be too dogmatic about class A - class A can sound too smooth and gluggy sometimes - go for speed and transparency, this will ultimately give you more satisfaction in the long haul. Try before you buy if possible.
One really good thing with the Rowland amps is that you can adjust the input impedance and gain to match your system. Their later 625 series would be on my list to try.