Answer: It's Chee, not Xi
You've arrived here because you used the incorrect spelling of Chee. Maybe you were given the name of the site verbally and you've taken a perfectly logical guess.
Anyway, it's HiChee and you've found their site!
Just click Here for the HiChee main page.
Xi is the fourteenth letter of the Greek alphabet and a really useful word in Scrabble.
Chee comes from the word Cheehoo, Hawaiian slang originating from Samoan culture. It's an expression celebrating something.