I'd like everyone to elaborate on what they mean on "intimate and engaging mids".
I mean, while I can't speak for the AKG 70* variants, I'm here listening to the SR-Lambda as usual, and I find music quite intimate and engaging already while having the trademark Lambda vast soundstage. Couldn't say the same for the SR-202, though; mids are noticeably recessed, at least with an SRM-212. The general sentiment amongst Stax enthusiasts is that the original Normal bias SR-Lambda is as good as it gets for midrange 'til you start shelling out the big bucks for Omega-series flagships.
Maybe it's because I'm "engaged" more by the music than the headphones I'm wearing, for all I know. I mean, headphones do help bring out certain parts of the music, but if the excitement wasn't there in the music to begin with, then no set of headphones is going to help with that.
Intimate can also be taken to mean narrow, closed-in, etc (not quite congested though). It's a sound-staging trait primarily - think about how a Grado or the ESW9 or some of the various Koss dynamic headphones will stage compared to some of the AT full-size cans or Sony full-size cans (which are "wide" or "spacious"). Planars are kind of a wrench in that (because they radiate differently) - you get a planar wave hitting your ear, instead of a conical one, and this changes the sound-staging characteristics of the cans overall (your entire ear perceives the same signal as a "wall" - Tyll actually wrote an article about this relatively recently).
Engaging is basically a mid-range emphasis in the presentation (but not over-emphasis). Bring them together and you get a relatively forward and direct presentation of the mids, and assuming nothing else is totally wrong about the cans in question, the voicing should be pretty spot-on (the RS-1 is a good example of this). Of course there's no single trait that absolutely indicates good mids or bad mids in a given can - it's the result of many things being done "right" all at once. And this isn't to say that cans with a wide or spacious stage can't be good, but their voicing is usually somewhat artificial (for example cans with S-LOGIC sound good, image wonderfully, but have a degree of artificial-ness to them).
And yes, the voicing and mixing of the source material absolutely matters here (be it mixing in a movie, or a game, or music).