That all said, my only reservation about the 598 is the rather large phase shift which could potentially affect positional cues depending how they are processed by the game/sound card... but I'm really just picking nits at this point.
It's always a crapshoot trying to get stuff up here in Canada. Do a search for "canadian companies" for a thread of mine listing a bunch of Canadian retailers. Otherwise, keep an eye out on the sale forums here or on canuckaudiomart.com
In my mind (ear?), engaging generally refers to the more visceral impact of music, which for most people comes in the bass and highs. A solid impulse response as well as quick decay time are also factors, but these concepts are harder to understand without some further reading. In an overall sense, "engaging" is simply a subjective measure of how well the headphones grab your attention.
That all said, don't get too caught up in what other people say. Head to a music/electronics store and try out a few headphones for yourself. Pay attention to instruments and what parts of the frequency spectrum really get your attention.
Get the cans first, listen, enjoy. After you become accustomed to their sound, try plugging into a receiver and see if you notice a difference. If not, then continue on your merry way and don't worry about spending any more money on diminishing returns. If you did notice a difference and feel it was significant enough to warrant spending more money and yet having more things in your pocket, only then should you consider getting an amp.
