It really depends on the music you listen to, and how much you value lower bass vs upper/mid-range. With ~90% of the music I listen to, the BS2 sounds much better than the Level, not even close. To me, where the Level ever so slightly beats the BS2 is with complex, high and mid-range heavy music (most classical, some acoustic and singing/piano-y jazz). I've never considered myself a "bass-head", but I find on most music (rock, some jazz, pop, electronic), I miss the BS2's punchy, controlled bass. The Level reminds me a lot of the BL6000s - "great for its size", sounds great for some music, but really lacking in the bottom end.... which isn't surprising when you look at the Level's design - it's only ~2 inches thick. I've really only listened to the Level in it's upright position.
I've never heard the Beolit 15/17. My guess is it would sound quite a bit better in the upper registers, and maybe a little weaker in the lower bass, but the bass it does provide is probably much better controlled. When it comes to value judgements, that's up to you. If Beolit sounds anything like the M3, I'd say its totally worth it, but, again, everyone values money differently.