There are a handful of manufacturers that offer headphone 'interface' units that allow you to drive headphones from a conventional amplifier's loudspeaker taps. They are inexpensive (compared to a decent tube or ss headphone amp) and shouldn't be considered a permanent solution. But could be an an inexpensive way for you to try out headphone listening without spending a lot of money on gear.
Driving a pair of low impedance headphones directly from a conventional preamp can also work while you're just in the "proof of concept" stage ;~))
Driving a pair of low impedance headphones directly from a conventional preamp can also work while you're just in the "proof of concept" stage ;~))