Contrary to what some have tried to say here, the Proac tweeters are not "glarey" (sic). They only sound harsh with crappy equipment upstream. (CD, pre, amp or cables) I have heard them sound great with the proper electronics, including transistors.
However, as others have said, Proacs are power hungry, so if you want to use a tube amp, it should have some good power, especially if you want to listen to them loud.
However, as others have said, Proacs are power hungry, so if you want to use a tube amp, it should have some good power, especially if you want to listen to them loud.