The KUL ES-87 appears fairly normal, capwise. The only thing I couldn't guarantee without personally touching it or seeing pictures of this, which I haven't, is the stem spacing on the spacebar. I'd wager it's common, but I'm certain someone here has purchased one and can help you better there.
For the 6GV2, the caps are what we call OEM profile. They're a fairly tall set of caps. Most caps you'll find around here will be shorter in height, such as SP's DCS profile or Cherry/GMK's Cherry profile. It's possible that the caps that come on the KUL will feel similar. Perhaps try them out before jumping to another set that you might not need. They will most likely be the same OEM profile, so if that's what you're looking for, you're covered there. If it's the texture, well you'll just have to touch them yourself to see that. I would assume they're pad printed, possibly with a coating over them to allow for some extended use before wear. I know what you mean about the grime. I had a Daskeyboard as my first keyboard, and I noticed the same. Doubleshot or dye-subbed caps would be a better fit for you here.
As far as PBT goes, there are a couple options. If you're looking for dark grey PBT caps with dye sub, look into the sets that IvanIvanovich ran not too long ago. They seem like they'd be the perfect fit.
http://geekhack.org/index.php?topic=50935.0 They will be Cherry profile, so shorter than you're used to. Also, I believe the GB is closed, so you'll have to peruse the classifieds, at least until you meet the requirements to post a WTB thread there. These caps will feel different in texture than what your current caps do.
DSA profile caps are a completely different monster. The caps you're used to are considered sculpted, meaning each row has a different height, and this lends to that sort of stair step effect on the keyboard. DSA caps are all one height, so a keyboard would appear flat with them. But yes, if you wanted to go this route, standard base and standard modifier set would suffice.