k2 is a great component but there is a other CCK nammed "jSeblod CCK" (www.jseblod.com) which is very powerfull because it's suitable with many extensions, like Virtuemart, K2...
jSeblod CCK is GPL and no-commercial. I build with jSeblod CCK a content type with 154 fields. Yes, it's a lot but my client need. jSeblod CCK do this perfectly. I haven't try with K2, is it possible ?
Thanks