Why a headphone amp

There are some people that use a poweramp for headphones. The amps are usually low power tube designs, not high power SS.

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 ;~))

Bigsam2, I have already Benchmark DAC1 with good headphone amp built in, but I bought separate headphone amp for convenience. DAC1 is across the room and requires long cable that is easy to trip over. In addition switching off main amp would require fiddling with switch on the back of DAC1 and possibly switching to wrong full volume position (I use its volume control - connected directly to power amp) or switching off power amp, that does not have power switch. My wireless server is next to my listening position and the best solution for me was to buy headphone amp/DAC. I got OPPO HA-2 and it is amazing with Yamaha HPH-200 headphones (another gem). It has asynchronous USB, SPDIF, DSD and analog inputs (I use USB). It has headphone and analog out. It uses SABRE 32 bit D/A converter and discrete output stage. Clarity is simply amazing (better sounding than Benchmark DAC1). It is also portable (has lithium battery built in) and works well with supplied ON-THE-GO USB cable with my android phone. My main computer is Mac Mini. It does not require driver. $300 is a little high, but it had great reviews and looked beautiful - wonderful packaging (I don't work for or sell them, in case if you wonder).

https://www.oppodigital.com/headphone-amplifier-ha-2/

Look around for a used Grado headphone amp. Get the battery operated one. A friend has one and loves it.

I applaud your inclination to "get some nice headphones." Personally, mine see far more action than my main audio system, as my wife is not an audiophile (imagine that). However, I have a long history of looking (and finding) ideal headphones. Your amplifier question has probably been well-answered by earlier postings.

My advice is simple: Try to attend an audio show. It will save you much frustration. They usually allocate a large room exclusively to headphones and headphone amps. Find the phones you like and invest in a quality headphone amp. Any of the phones you audition will be fine, but try to find one that you can live with long-term. I recommend Stax, but they are not for everyone. Good luck in your search.