You'll find Tom that your RFC Canterburys aren't actually that power hungry and won't draw a lot of current at all, even at modest to loud listening. Minimum impedance is 7.4 Ohms at low frequency and they're nominally a true 8 Ohm load with a sensitivity approaching 92dB/1w/1m at 1KHz, and slightly more, about 93dB/1w/1m at cab tuning (low frequency). The worst case phase angle is around -42 degrees at 60Hz but as impedance is close on 12 Ohm at that frequency, it's not that demanding a swing in terms of current. A good 25 Watt PP valve amp, or a 20w to 30w SE amp using a little global negative feedback will drive them no problem at all. 35 to 40 Watts PP is better. Even a 10wpc SE amp will drive them to pretty loud levels but just wont provide the control or dynamic swings of something with more power and lower output impedance. A modest valve amp like that wont provide the concert-hall dynamics you get with your monster Radford though!
I will be treated to a TRON Atlantic SE amp in the system just for a bake-off of various components with Graham in the not too distant future, so it will be interesting to hear just what 10 Watts of pure class A loveliness can do with them!