RAMd®d wrote:
First, whether or not you'll hear any improvement with a headphone amp depends on your audio acuity.

Second, even if your ears are good enough, you're working with mp3 files. Any improvement in hardware may reveal the compression artifacts in those files, especially if there are any flaws aside from compression.

Third, though Apple uses really good (read: not crappy) DACs, their headphone amps could probably stand some improvement, as could those of most audio devices, especially in portables. So you'll want to use Dock connector output to the amp.

Fourth, as you've found, quality external headphone amps are pricey, especially the AC powered amps from headphones.com.

Fifth, to get the most out of a quality headphone amp, I think you need to get better 'phones than the 280s. Not that they're bad, but improving any link in a performance chain often "weakens" one or more previously strong links.

It's not always hype when sellers say "to get the most out of these headphones, you need a good hp amp". Great 'phones need a great source if you want great sound.

There are real, audible gains to be made when going hi-fi. But some of us reach a point of diminishing returns sooner than others.

If or when you get an amp, try to avoid the placebo effect. Many so-called "audiophiles" don't really know that they're talking about in terms of absolute performance. Their music sounds better because they paid big money for esoteric products. The Placebo Effect.

If you can afford it, it doesn't hurt to by "more than you need" in audio gear. You know you have some headroom (npi) to grow into it. I do this a lot. Listen to your new iron exclusively for a protracted period of time, then go back to your old stuff and critique the sound. This will help you identify more subtle differences much more easily than flipping back and forth.