I'd suggest taking a look at Griffin Armament. The few people I know that have handled their cans have been impressed, and their pricing is fantastic. I had an at-length email conversation with one of the owners, and he seemed to have a really good head on his shoulders when it came to design and manufacturing.
$650 for a QD suppressor INCLUDING the $200 tax for the Form 4 is a ridiculous price. They are also taking preorders for their M4SD II, as well. It will be 316L stainless for the body and 718 inconel baffles for under $800. I plan on adding an M4SD II to my SBR as soon as personal finances allow.