It is not my intention to discredit any manufacturer. But here's a little known fact. Semiconductor companies in their quest for faster time to market has produced reference designs that include PC board, software and sometimes even FCC certification. The intention is for the customers to have a cookie cutter design block that manufacturers can add value to and I'm sure some of them do add their value.
Here's an example. http://www.xmos.com/products/reference-designs
This is an USB DAC design. It has all the hardware and test points needed. It can also perform USB to SPDIF conversion in addition to being a functional DAC. As with all reference design, performance is published. The jitter performance is 4.6ps. This board can be purchased from Digikey for $149. Ah, it is also in two layer board in the size of a credit card. XMOS target customer are industrial application like Pro audio. So their chip is embedded with a 500MIPs 6 core processor. In most consumer application this is an overkill. In theory, you can purchase this, put in your enclosure and sell it as an audiophile product and charge $300.
I do not recommend anyone buying this product because it is not consumer friendly and it may or may not even come with an enclosure. In addition, you have to load the firmware before it works. None the less, the point I'm trying to make is it seems like USB audio is complex but it is not. And there are many way to add value but there is very little value to add at the media (USB) side. Even at the play clock, how much can you improve with 4.6ps. Maybe at $1,000, the jitter should be 0.5ps?