But I’ve heard that Planars and tube amps don’t mix.
Yes, that is typically the case with output transformerless (OTL) tube amps and harder to drive planars. Then there’s exceptions like the Valhalla 2 being able to drive some planars just fine.
If you really want to use a tube amp with planars, you should get a transformer coupled tube amp. Doesn’t matter if it’s balanced or single ended as long as it has enough wattage. 1W into 50 ohms, which is roughly what the Magni 3 outputs, should be plenty for most planars.
Here’s an example of the Hifiman HE6se V2 being used with an Elekit TU-8200DX. One of the most power hungry planars driven loud enough with room to spare on a tube amp.
Fostex T50RP* since they typically go for $170 now. Can sometimes be found for around $90-$130.
*They definitely need mods to sound good, so that’s about $5-$30 depending where you source your modding material. Then another $10-$80 for the ear pads. And another $100-$200 for an amp/DAC since they actually require one, especially after the mods.
If done correctly, they can have a similar midrange conpared to the 6x0 line with actual subbass, extended treble, more soundstage, instrument separation, and better imaging.