Imp-
I'm not sure if you're still looking for audio books, but as a fellow audiophile I'd highly recommend Brandon Sanderson's Mistborn trilogy. It's not as rich as ASoIaF but it does have the distinct advantage of being finished and it's by far the best work I've heard Michael Kramer do as reader (he also reads the male half of the Wheel of Time Books) and it's a hell of a fun ride. Some good twists and turns (though I actually caught most of them, used as I am to super close readings thanks to joints like this one).
The Wheel of Time audiobooks are pretty good, though they suffer from the same isssues as the series as a whole in that really become interminable around book seven or so... Of course, if you're like me, by that point you'll be pretty hooked and therfore willing to continue through the tedium just to see how the whole thing wil resolve itself. But the will keep you listening for a while, so they've got that going for them...
As for other audio books in the genre I've enjoyed, I'd really reccomend Sussana Clarke's Jonathan Strange and Mr Norell, it's kind of Jane Austen by way of Harry Potter, but it's definitely for grownups. It's beautifully written as it moves from a Victorian comedy of manners to something deeply unsettling and ineffably creepy. It's only one book, not a series, but it's like 30 hours long so it'll keep you busy.
There are some realy great Neil Gaiman audio books out there as well (he's the rare author who's not a complete disaster reading his own stuff). Once again, not series but stuff like American Gods, Neverwhere, The Graveyard Book, and Stardust have all made audio books I've greatly enjoyed.
I'd be remiss if I didn't mention, cliched as it is, the Harry Potter series as well as simply spectacular audio books. If you think Roy Dotrice make ASoIaF come alive, wait until you hear Jim Dale, the work he does on that series is really superb.
I hope you find some of this useful...