I've listened to Grados for over 15 years now and, even though I have a pretty decent stereo setup, sometimes I still prefer music through headphones. They're great headphones that are pretty easy to drive, but they're treble-laden compared to the many other cans I've listened to. (I think the hype 15 years ago was that they were "crisp", now they're considered "bright".) They don't lack bass (I love my Grado's bass response), but they have a definite overemphasis on higher frequencies at typical mid-range listening levels. A frequent way to compensate is to use a poorly-designed tube amp with lots of rolloff at the top...
I actually spent almost a year trying different phones before I decided on the HP-1s, and in retrospect the decision process was almost comical. I found at least 10 different pairs I would've been happy with at a variety of prices, but I settled on these because of the tank-like metal construction and I could get a demo pair at 60% off. Since they've lasted this long with no signs of quitting, they were a good buy.
I've found an external amp isn't a bad idea, as many of the headphone outputs I've used haven't been very good. The most common problem has been rolloff at the low end (including finding low-value "coupling capacitors" in series with the jack), and I've even run across a couple which had audible distortion driving anything other than exactly 8ohm or very high impedance headphones. Headphone jacks frequently seem to be an area in which manufacturers spend as little as possible.
(On the other hand, if your equipment has a decent headphone output an external amp won't do anything for you. And a super-expensive headphone amp won't work any better than a reasonable one, of course.)
My advice is simple: if you're considering a major headphone purchase, always listen to as many cans as possible before buying... which almost always means finding a friendly local dealer. What works is more about personal taste than anything else, and you may very well find a $30 pair which fit and sound just as good as (or better than) those $400 Grados or $insane Stax.
For example, Grados are not exactly known for their comfort over long sessions. (One honest reviewer said something like "it feels like my ears were squished in a vise", and the HP-1s did feel the way the first few wearings.) Beyerdynamics were the most comfortable cans I tried, as they had really nice pseudo-felt pads instead of the foam or fake leather used in so many others. (Mileage will vary; do not drive car while wearing headphones over eyes.)
One issue I have with the current Grado designs is that they feel kinda fragile. I wouldn't recommend the RS-1s or RS-2s; the wood looks nice, but I gotta wonder how long they'll last and they just seem overpriced. The clips holding the speakers on the plastic models have always looked like they would break pretty easily, and a friend of mine had continual problems with the metal pieces coming out of his SR-80s. They definitely are light, though, and are sturdier than some of the cheaper models on the market.
Just some advice from a "serious headphone user" who hates the snake oil as much as anybody... avoid the hype and the high prices, and try lots of different cans before making a purchase.
