Sure, most AV receivers have "good enough" built-in headphone amplifiers, which are fine for occasional listening.
But if you regularly listen to a decent set of headphones over your home theater system or computer, I recommend moving up to a high-quality headphone amplifier, like Benchmark's DAC1 USB ($1,275).
AV receivers' headphone amps, even on $1,000+ models either sound anemic, with little or no bass, or they're muffled sounding things. Whenever I review high-end headphones, I always plug them into an iPod, AV receiver, and a dedicated headphone amplifier, just to see how they perform in different contexts. But headphones always do their best when plugged into a good headphone amp.
Benchmark is one of the few manufacturers of professional audio gear that has consistently wowed audiophiles. The company offers a range of headphone amplifiers, and I reviewed the Benchmark DAC1 USB when I tested the Denon AH-D5000, Grado GS-1000, and Ultrasone Edition 9 luxury headphones for Home Entertainment magazine.
The Benchmark is more than just a headphone amplifier; the DAC1 USB also features a 192kHz/24-bit digital-to-analog converter (D/A) and, you guessed it, a USB input. The digital converter plays a big part in this product's sound. The DAC1 USB is compatible with Windows and Mac OS X operating systems.
The amp, made in Syracuse, N.Y., measures a compact 9.5 inches by 1.7 inches by 9.3 inches. I squeezed the little guy onto my desk next to my monitor. It's a beautifully crafted device, built to last a long, long time.
The DAC1 USB/Grado GS-1000 combination really clicked for me. The sound seemed to surround me, with terrific depth, high frequency "air" and detail were superb, but the midrange was warm and natural. Grados have always had an exciting sound, and now with the DAC1 USB classical music sounds more refined. Bass is deep, yet more controlled and precise than ever before.
Going back to the receiver, the GS-1000 sounded veiled, blah, and utterly boring. Point being, don't bother buying a set of $500+ 'phones unless you're also going to get a decent headphone amp.
Before you comment about the DAC1 USB's hefty price tag, I'm not claiming it's the only way to go. It's just one I've recently tested. I heard the Woo Audio WA3 ($470) a few years ago and was blown away by the little tube amp's sound and build quality. It's made in New York City.