K604 was the only agency I tried, mainly because there was no reason to go anywhere else. I only used their "branded" girls (says Korean604 on the photo), mainly Korean and Japanese. Perfect GFE with all the usual acronyms, there's some add-ons if you want, the dongguan (DG) service is the most inclusive for the price.
It sounds expensive when you look, but the exchange rate is 72 cents, so a pretty hefty discount. Perb dot cc is the real forum you want to check, I left some comments in a thread called Boli K604 - Nuru. I also reviewed a few girls there on TER, top shelf!
I know it's sounds TGTBT, but almost all the girls were super cheerful, no rushing, shower with preview, very patient, did what I wanted, and somehow were still GND with pro skills. If there's a mongering Utopia, this is it.