Hey Rja-
Good for you and your wallet! For me the differences were not subtle...and mostly in the vein that Bobf mentions.... but that what makes a horse race.
As a matter of fact, I preferred a mixture of the Extreme and the Revelation to all Revelations. In a nutshell, I love the delicacy and detail of the Rev's, but missed the soul of the Extremes. It was like the difference between listening with your heart versus your mind. I also think the sounstage is bigger with the Extremes and that's something I really enjoy. The Raptures brought it all home in spades (like the familiarity of the musty smell of your granddad's sweater in the fall...comfy and rich with closed-eyed memory and emotion...but I digress) along with the sonic improvements I mention above.
Same family, as Bobf says, but a different animal...and evolutionary leap...a genetic shift instead of the normal drift...don't get me started on intelligent design; after all, i am inertia man!....but i digress (again!).
Bobf-
I have the Raptures in my main chain and a pair of Edens to my headphone amp and a pair of Extremes to my Squezebox. I would love to have all Raptures, but just can't swing it right now. I do prefer the Edens a bit over the Extremes as they offer the same soulful and natural presentation without the bloom....All the attributes are still there; detail, extension, control, pace, clarity and spatial presentation, but with enough less bloom that it seems to be a quieter background. Definitely a killer bargain and great cable. If you like a bit of midrange bloom or your system veers to the clinical, the Extreme may be your best choice.
No telling really, as rja's experience reveals. Listen and learn and let your your ears be your guide. (might just save you some money!) some ears, like spock's, really point the way (might just save you some time!) and other's just keep hungering....especially as they fall into the aging category....wearing slippers and a bathrobe....and an old sweater....
BMW 3 series? Zippy! Maybe the 5 series?....no m's in the 7 series, although i saw an m6 on the highway that had me drooling on my tie. Audio is definitely a less expensive hobby; at least that's what I keep telling my wife!
Gotta run, enjoy the tunes!