I have a pair of these and must say that they sound great with a tube amp.
They are way better than my Dovedales.
It may be that the purple tweeter is a bit hot, so the slightest bit of harshness is put right out there.
These speakers seem quite efficient and did shine with my Sweet Peach single ended driving them.
I would say that they would be worth a capacitor upgrade.
For me it was like listening to a poor mans Tannoy and they will show up any issues with the rest of the system.