If you’re going to spend $100 on a headphone amp and your interface is that old, I would just get a new interface. Even at that price the converters are going to blow away the ones in the Tascam and most should have a strong enough headphone amplifier, but you’ll have to do some reading to make sure.
I have a $100 Focusrite Scarlett Solo and I think it’s headphone amp can drive my 250 ohm cans… not positive on that though. Haven’t used it for a couple years.
Send the Tascam down the road bro, seriously
My cheapo, which is in some box somewhere, was like $80. It’s one of those 4 headphone things, I think from ART? It works well, but isn’t a critical listening device. It’s good for tracking where you just need the little extra power that a wall wart gives. There’s nothing wrong with it at all. It’s a little amp. It amplifies. It’s not ugly sounding.
For critical listening, I use the Avenson Audio headphone amp. It’s noticeably better than the headphone output on my Apogee Duet or UAudio Apollo. i.e. an untrained person should be able to tell the difference. I got mine dirt cheap, but in retrospect, I think it would easily be worth the $550 you see them going for used these days. I don’t think I would have believed that if you told me beforehand, but at this point I’m totally convinced. If you’re going to mix on headphones or do any kind of critical evaluation, I suggest going all out on the headphone amp. You’d be surprised how much more information there is when you listen through one.
Also, though, if you’re going all out, get a good pair of open backed headphones. Bass response is more natural than with any closed back. I use the Sennheiser HD-650 for that. The DT770’s are really for tracking, where I don’t want bleed into a mic, or want isolation so I can listen while positioning a mic. Also, one of those compensating EQ apps like SonarWorks is really nice to have when using any headphones.