I am also having the SF Grand Pianos but it's the older model. My first amp was the Arcam Alpha 10 and now I've moved up to Classe CAP-100 that is so much better than the Arcam in many areas. Although the Alpha range was long time replaced by Diva and FMJ series, they have the same old typical Arcam sound, polite and uninvolving. One of my friend has the FMJ A32 very much earlier and sold it late last year. He has moved up to Tag Mclaren AV32R-5R combo.
Anyway it is a matter of preference as some like it laid-back while some would prefer a more upfront sound and grunt. Nevertheless, I would advice you to go for a more powerful amp to drive your Grand Pianos. In my system, there is no denying that my Classe integrated cannot drive the GP's to its optimum. The GP's need huge power. I have tried the Krell KAV-300i to drive the GP's and it sounded little better with more authority and control. I believe the GP's will benefit more with more powerful amps. I am not biased towards ARcam but I strongly think that they wouldn't be able to drive your speakers too efficiently.
