Hi-fi digital front end suggestions for my system

Hi Latinsamba1
I just want to add alternative to above choices.
It is a Sonos system with Nixon Scott tube dac.
It is a easy almost plug&play setup
Easy to use with a very cool wireless controler.
Works with pc/mac - wmp and itunes.
I have it setup with my wireless 1T-bit hard drive.
A big plus of this set up is that you do not have to turn your comuter on to have access to your music library.
Nixon's tube dac makes the music a little less grainy/digital. This is only my opinion based on my own exp.
The whole setup will cost you about $1500 and if you decide to add huge ext. wireless hard drive - $300 more.
If you ask me how does it sound.....well... it sounds great.
It is at least as good or better then my Rega Apollo but not as good as new Prima Luna's ($2500) new CD player, which in my opinion beats everything up to $5000 and will be my next referance CD player.

I purchased over a year ago a Non-OS DAC called the Constantine from some gentleman in China. It is available generally on eBay around $300. (I've never seen one used). I have a Moon I-3 SE, Aerial 6's, AQ Bedrock, and a Consonance CD 120 CD Player. In addition I have a Dell PC as a dedicated source component.

The Constantine is made, I have read, by a company called Mhdt. My model offers USB inputs as well as the other two styles of digital, with switching (back panel) between. Powered by a standard IEC removable cord. It is hand-made, and a beautiful unit.

Well, what about the sound? I like it very much? As I have said, i have had it well over a year. I find it very musical and detailed at the same time. It throws a nice soundstage, and really doesn't seem to do anything wrong. For the price, it is a very good deal, and it holds its own with the DAC on the Consonance (which replaced a Jolida). I have used it for USB off the PC, and it is a plug and go set-up. I've also used it with a Sony cdp (quite an improvement), and with a Roku (quite an improvement).

The gentleman ships them very quickly and very cheaply. They don't come with power cords, but that would only increase the price of shipping and the unit. Lately, I've been thinking about buying a second one.

I know, when i first saw the thing on eBay, I was hesitant for a number of obvious reasons, but I have never been sorry I bought it. My feeling about all the talk between OS/Non-OS/1-bit and whatall is that the execution of the basic technology is more important than the technology itself. I think the Constantine is very well executed.

Now that both the Wavelength Cosecant USB DAC v3 (now with ASYNC mode) and the Benchmark USB DAC 1 and DAC 1-PRE support 24-bit audio at sample rates up to 96 kHz without the installation of any drivers or other special software. I am having a hard time choosing between them. My primary headphones are the Ultrasone UE 9 and the Grado GS 1000. Has anyone out there heard both side to side at any of the meets??? Are there specific advantages of one over the other?