They are reputable and have been around for at least seven or eight years that I know of ... I have spoken with them a couple times regarding different subjects and they seem to be reasonably intelligent and know what is going on.

Another resource for used vintage gear in the US is http://www.proaudiomarketplace.com ( Pro Audio Marketplace). For a subscription of $25 per year you have online access to a lot of pro audio gear ads and you can advertise your own gear. It's a great resource ...

I'd say so. I bought a preamp from them and it was in good clean shape when it arrived. Friendly on the phone as well.

I want to buy from there...is it reliable?
any experience?

I purchased a pair of API 312 cards from them last year and they were exactly as advertised. I got what I paid for without any notable problems.

Vintage King are good guys to deal with.