Karma is AFAICT a Chinese rebadger that runs out of a guitar maker shop about three blocks from where I work. They sound very similar to many of the group buy mics I've seen, though the enclosures are different.
If you're looking for mic to mod, the Karma mics are good choices. Their K58 tube LDC is a great mic for modders, IMHO, because it has an oversized body that you can easily sandwich other parts into (e.g. a large transformer). That said, the stock K58, even with a tube swap, still doesn't feel as nice on my voice as
my CAD M9. I think it really needs a different capsule to sound good on tenors, though I get the distinct impression it would feel good for altos or mezzos. It's a little too clean and a little too spitty, IIRC.
As for the SDCs, I've tried various cheap Chinese condensers (which the Karma mics are). They all have a certain characteristic sound to them---significantly rolled off low frequency and lower midrange response, flat across the mids, and a harsh, brittle presence peak as you start into the high frequency range. I highly doubt theirs are significantly better in this regard. I could be wrong, but I'd be surprised.
If you're looking for something under $100 apiece, the only thing I'd recommend in that range would be the Naiant family of mics. They're very accurate, so if that's what you're looking for, you've found your mics. Some sources need a little more warming up, and for that, IMHO, an MK-012 pair is really something to behold. The Oktavas are fairly warm sounding mics, not thin, harsh, or brittle like the Chinese mics I've tried, so they'll immediately sound very different from whatever mics you're currently using. Both the Naiants and the Oktavas are my first pick for a wide range of applications, and you won't regret buying either of them.
I wish Jon still made the MSH-4, though. Out of all of my Naiant mics, those are my favorites hands down. *sigh*
