You in particular should also benefit greatly from a SEP IRA. Expensive to run but lets you sock away much much more.

Actually Solo 401k lets you put away just as much if not more, and has a Roth option. But both are worth considering for sure.

What's expensive about running a SEP IRA? Are you referring to the fact you have to contribute to an employee's IRA as well as your own?

I had to jump through hoops and pay a specialized firm to administer. Maybe it no longer applies?

Both are basically plug and play now with places like fidelity or vanguard. Zero admin fee for mine.

Seconded on no cost with at least Fidelity. They start having reporting requirements at $250K of assets. They are also something of a pain to close if you have multiple participants.

I can’t say what happened, but SEP was always the simpler, cheaper option, nearly DIY compared to a proper 401k.