there should be an email address on the audio-gd site. you simply email and tell them exactly what you want and where you live, and they will email you back an order total with further instructions for paying.
as far as pacific valve goes - their version of the same product will cost 5 or 10 percent more. that is because they import the item, and then offer their own warranty and repair service. which means you don't have to send it back to china if it breaks.
also, pacific valve tests and burns in the product. and, with some items, they do minor modifications which they feel add to the performance of the item.
hope that helps....
