Ocellia speakers and power

25 watts or so is all they are rated for if I recall right. The speaker likes a bit of power so I would put as much as you can on them. We used our S-30 on them to very good effect. Any smaller tube amp should do the job; a lot will depend on your room and your taste in music.

10 Watts of SET fills a 12x12 foot room with plenty to spare.

I use an 8 watt SOUGA amp and find it fine, listen in a large room and sometimes at very loud levels.

If you go to the PHY website it has all of the info you need. The "admissible" power rating was fairly low, at around 50 watts. The sensitivity - depending on the driver used, is 97 to 98 Db, I assume for the usual 1 watt at one meter. Given that and what appeared to be a very friendly impedance curve this speaker looks like a dream speaker for any S.E.T amp that you like.
As an aside, from the graphs these wideband single drivers drops off very steeply above 10K Hz and it also drops out below 50 Hz.
None the less I imagine your speaker will sound fantastic with a good tube amp of virtually any power rating.
I apologize for waxing poetic but I just read a 6 Moons article about PHY.
BTW What is a SOUGA amp?