Lurk650
Headphoneus Supremus
Funny you should say that because I just added them to my wishlist less than 5 minutes ago. If you say they are better than the K4 I can hardly pass them up. I was actually thinking about wiping everything from my wishlist and going for tk12/13 but still undecided.
I feel they are bit better, better quality bass that goes deeper, mids are less in your face and vocals (esp male) don't have that extra bass to them (not as thick sounding), treble is a bit brighter. Sound stage is wider and a bit deeper. More clarity, natural sounding than the K4 (which is still a very good IEM). TK12/13 will still trump though