Sonus Faber Amati with ARC Reference 600 Mk II

I am using my Amatis with ARC VTM200 monoblocks. Sounds great...

I wouldn't hesitate to pair the Amatis to the ARC Reference 300 monoblocks. Less capital investment and maintance.

Have found that apparent overkill is necessary if you're using SS. Less overkill is required if you're using tube -- BUT it's advisable to use a detailed, dynamic (fast) tube OR ss.
If you already have the 600's well, why downgrade?

If you don't, then you can get away with less power (BUT not cheap power IMO)... OTOH if the maintenance cost of the 600 is the issue, as you mention, I'm not sure a smaller tube will be THAT cost effective maintenance-wise!
Wouldn't the acquisition cost of the 600's be more of an issue??

The best Amati set I ever heard is with VAC Avator EL34 integrated amp. It doesnt require tube power stations to drive. Remember, Musica..........the matching gear for SF Classic series, is just solidstate amp with 50w per channel output only.

If you owns WP, it is sensible to use power station to run the speaker well.