I've tried KHMountain with no luck. I've got my order refunded three fucking times.
The first one, there was some event in China that got their customs more busy, and my package was supposedly stopped there (no guns, just gear and accessories). I've got a refund.
The second one (I reordered the same items), I was left without comms. I made a PayPal dispute after 3 weeks, then they started answering me a week after the claim. They asked me to cancel the dispute so they could process the order. I told them I preffered a refund, and I finally got it way later.
I gave them a last chance, simply since they had a bunch of items I couldn't find anywhere else. This time, I didn't order everything I was interested in; I just purchased what I couldn't find. Again, no comms or whatever, ever. They refunded me without comms just the day before the automatic dispute ending when I threatened that this was their last chance before a claim.
In short: don't even consider KHMountain.
Some HK retailers I've had good luck with (not always perfect, but overall a good experience)
-PX-Airsoft (Prompt shipping, good prices, but a bit slow for customer service)
-eHobby Asia (A+++)
-G-Military (They never answered my questions by email, but I had some good deals and everything was shipped fast. Shipping was goddamn cheap too)
-Airsoftpark (Good, fast comms, free shipping, very helpful to find items they didn't have listed)
-EBairsoft (Variable communications, was sometime fast, sometimes slow. Same thing for shipping. Overall good prices)
As it was said by the others, start by looking on the classifieds and with the canadian retailers. You can also find very good deals there.