How much Tube power to Drive Heron-i's?

I've been driving my Heron-i's with the 200wpc (SS) Sunfire Cinema Grand. My second system uses a small pair of Audio Physics with a small pair of monoblock tubes.

I hate to admit it, but the sounds is comparable. Now, there are a lot of reasons for this, but ultimately, I would like to try some tubes with my Herons.

The catch? I don't want to spend more than 1500.

So how much tube power do I need and what do you recommend?

take care,
John