Well IM and the like are making pure dance music. It's not really there to be listened to on its own, though of course you can. Shpongle's Simon Posford also makes dance music under the Hallucinogen name, and it's very good too IMO but once again it's music with a purpose. Shpongle, on the other hand, has a lot more cross-genre appeal, and yes, once upon a time I was also Shpongled quite thoroughly, breaking me out of the classical and prog rock I was into at the time. Of course losing my Shpongle virginity also accompanied going to a three-day psytrance festival and everything that this entails, so you can imagine just how thoroughly I got into it. So thoroughly, in fact, that almost 10 years later now I'm still very much into the scene, and electronic music continues to be my main area of musical interest, though perhaps not quite to the same extent.
Shpongle make serious music - perhaps music that's every bit as significant as anything that any renowned classical composers made back in the day. It's one of the few acts that I can label as "brilliant" and not make any kind of disclaimer afterwards. Well, save for one maybe - they've been in a bit of a creative slump lately (the last two albums have their moments but are in general a notch below the first two), but that is to be expected - the last two disks are out due to fan pressure; the artists themselves feel that they've said everything that they need to say two albums ago.
If you're looking for stuff like Shpongle - as you can imagine, there isn't a whole lot. But, there are some suggestions I can throw out:
OTT - Blumenkraft. OTT actually co-wrote a lot of Shpongle stuff together with Simon and Raja Ram, and uses a lot of the same studio musicians and vocalists on his project, so as you can imagine, it has a similar feel. This is the only OTT album that I really like, the followup was kinda meh IMO.
Shulman - pretty much every disk, though Random Thoughts is probably my favorite. Shulman is a bit more downtempo compared to Shpongle, but has a very good sense of classical melody. Really, really good stuff but a bit harder to get into.
Maneesh De Moor - Sadhana. I really don't like a lot of the meditation music Maneesh De Moor makes, but this album seriously takes a page from the Shpongle book, and is IMO brilliant. Story-driven, progressive electronic music, and rumor has it that once upon a time, Maneesh De Moor was in an Ayahuasca ceremony, and under the spell he heard this extraordinary beautiful music, and for the next several years he was on an obsessive quest to try and recapture and replicate what he heard. The end result is this album, and the feel of it seems to support this.
Nicholas Gunn - Breathe. Not electronic music per se, but I'll be damned if melodically this disk isn't similar to Shpongle, especially the first track. Oh, and Nick Gunn is one of the best flutists out there, too, sounding a bit like Raja Ram with better technique. If you want acoustic Shpongle this is it.