Are Headphone amps worth the expense?

There is a headphone jack on my Luxman 509u integrated amp, and my Beyerdynamic T1's sound wonderful when plugged-in. How does it compare to a dedicated headphone amp? I am not sure how much better a high quality dedicated amp would be, but as I am quite satisfied with what I have I am not going to lose any sleep over it.

Can a headphone amp be fed by the "line out" or "tape out" of a conventional preamp?

I do say tape out in my post. If you use the line out, make sure you don't drive the preamplifier volume up to high. The headphone amp would distort too high a signal. It should be an unamplifiedoutput.

A good quality headphone amp with god headphones will blow away most receivers with a headphone Jack. Thi receivers or intergrateds with a phono stage. You really need to look high and low to find one as good as a standalone, but I have heard they are out there.

thanks for all the advice

I think they are. I have read that the headphone outputs on high end equipment often are not up to par with the same quality of output as the device. I built a cheap cmoy headphone amp using a Burr Brown 2227 opamp. I use it with
Grado SR-80 phones and WOW. I didn't believe the sound. I can't believe that high end phone amps do much better. I took my homebrew amp into a high end audio shop and they said it sounded like a 250.00 phone amp. You might consider building a cmoy amp. Many places on the internet with info. Dean