Hey Dee, it's in the right forum. No clue about the XBA-3 as I've never heard them, sorry man!
I have the Sennheiser IE80 (not sure why you'd want the IE8, as it's been discontinued - the IE80 is the same thing, but tweaked a little for better sound, while retaining excellent bass slam and soundstage), and have heard the SE535 for a brief 10 minute audition at Jaben. Obviously it's an unfair comparison, but my thoughts are as follows:
I think your 'lots of bass' requirement rules out the 535, which has excellent detail retrieval and pretty good imaging, but a smaller soundstage... Furthermore, your request for 'pronounced midrange' rules out the IE8(0), which does not have a forward midrange at all to my ears. I suppose you could pick depending on which one you like more. Also the 535 isolates way better than the IE8(0).
Alternatively, since you didn't want to settle for an in-between, you could try an IEM which does both well in your price range! I'm not an IEM expert, so perhaps try ClieOS or ljokerl's threads on those.
Based on your criteria, I feel that you will probably find the IE8(0) is severely lacking 'pronounced' mids, so perhaps check out the W3 (slamming bass, not sure about the mids but I haven't read that they're bad) or, if you're going high-end, the PFE232 (changing the filters can increase the bass, and the mids are excellent according to planx's detailed review). These are not recommendations - I have heard/own neither - just more options.
Personally, I love my IE80. I think its midrange is just fine - sure, it's shrouded by the bass just a shade (I listen on bass level 2/5), but still quite rich in its own way and satisfactory to my ears. If you did wanna buy an IE80, it's pretty cheap on amazon.de, but genuine (I have claimed an official warranty on its cable, so it's definitely legit).
Edited by StyleElements - 12/31/12 at 7:43pm