I looked up my notes - the OT-2 (Stereomour/SEX output transformer) operating as an 8K transformer (SEX) saturates about 2.4 watts at 25Hz, which is 4.8 watts at 35Hz or 9.6 watts at 50Hz. At 4K ohms (Stereomour), it's 2.4 watts at 18Hz, 4.8 watts at 25Hz, 9.6 watts at 35Hz, and 19.2 watts at 50Hz. Measured inductance was 45H at 350 Gauss, gradually rising to 265H at 7000 Gauss (as high as I could go at the time).

For comparison, OT-5 in Kaiju at 3K ohms is good for 8 watts at 22Hz.

These calculations are for 29-gauge M6 grain-oriented silicon steel at 13,500 Gauss flux density - moderately conservative since power transformers will sometimes push the M6 flux density to 16,000 Gauss.

A quick look at that Lundahl shows the primary is always the same, at all nominal impedances - only the secondary taps change. That's exactly the same as OT-2. Looks like it will handle about 10 times as much power as OT2 at any of the above impedance/frequency combinations. I see a rated 150 henries for the small gap (parafeed), but at an unspecified flux density. It's common to measure this at a high flux, but I don't know how Lundahl does it.

I estimate from the specs that Lundahl does their power rating at 16,000 Gauss, which is about 40% more power than 13,500 Gauss, but - again - I don't have specs on their core material, and I'm making some guesses.