If you plan on driving them directly from your iPod -- without a seperate headphone amp -- then your options are limited. Grado SR60 is one of the few audiophile headphones that can do the job, and do it well. You could also buy the SR80 or SR125 and still be OK but you might not hear the difference. Grados can sound a little bright and hard though as you move up the range. The Sennheiser HD555 is under $200 and it's warmer, perhaps more sonically and physically comfortable.
Here's what I would do if I were you and a headphone amp were out of the question. The jack on your McIntosh preamp is probably pretty good. Since you're going to be listening to headphones exclusively, get the best set of phones you can afford. Your iPod will NOT be able to drive either of these: the Sennheiser HD600 and AKG K601 or K701. Both are slightly above your budget but worth it. The HD600 is a gorgeous sounding set of cans that's exceptionally smooth yet detailed, while the K601 and K701 are more spacious, a bit thinner but also more extended in the bass and treble. Both are extremely comfortable.
Now, what about that iPod? Well, either dock it and run it through the McIntosh or buy a set of iGrado headphones for $49 and use them exclusively for the iPod since audiophile cans tend to be too big and bulky for travel anyway.
Here's what I would do if I were you and a headphone amp were out of the question. The jack on your McIntosh preamp is probably pretty good. Since you're going to be listening to headphones exclusively, get the best set of phones you can afford. Your iPod will NOT be able to drive either of these: the Sennheiser HD600 and AKG K601 or K701. Both are slightly above your budget but worth it. The HD600 is a gorgeous sounding set of cans that's exceptionally smooth yet detailed, while the K601 and K701 are more spacious, a bit thinner but also more extended in the bass and treble. Both are extremely comfortable.
Now, what about that iPod? Well, either dock it and run it through the McIntosh or buy a set of iGrado headphones for $49 and use them exclusively for the iPod since audiophile cans tend to be too big and bulky for travel anyway.