Speakers to pair with the Ars Sonum Filarmonia tube amp?

http://www.reference3a.com/decapo.html#info

http://www.reference3a.com/reflector.html
I would suggest you listen to the above referenced speakers with your Filarmonia.

There's probably other good speakers that will pair well and have the synergy with the Filarmonia. The manual states that your speaker choice should not dip below 4.3 ohms (I think).

You may want to ask Rich at Signature Sound High-End Audio what speakers he knows to match well with the Ars Sonus Filarmonia.
He is the US distributer.

Personally I think you cant go wrong with a pair of Merlin Music TSM Magic addition with the master RC network and Cardas Clear Light cabling. You may be able to find the speakers on the used market.
Signature Sound services them.

http://sigsound.com/merlin-tsm/ 

ProAc should work well. You may want to demo a pair.

Keep in mind that the Ars Sonus Filarmonia has an 8 Ohm x-former tap only.

There is a fantastic deal on a pair of the newest Reference 3A Episodes on Audiogon right now, with FREE shipping. They would be a great match for that amp. An easy 8 ohm load and 92db/watt/meter efficiency. I already have a pair that I have been enjoying for 5 years now, and I'm still tempted to grab them at his asking price!