well, I paid about $1200 or 1300 for mine, new. I got a deal though, because it had been opened and used for a magazine review. I'd imagine that I'd ask around a grand for mine, if I ever decided to sell it (but, to be honest, I can't imagine deciding to sell it any time soon). I've compared it directly to the benchmark DAC1, and prefered the 901. obviously, I'd say it was worth it to get a 901 over a DAC1. I have never heard a Mytek DAC, so I can't comment (although based on the quality of their a/d units, I'd guess it sounds great. The real problem is, where are you going to find a used grace 901? at this point, the only way I'd ever consider selling mine is if I decided to buy an m902 to replace it. I don't recall anyone ever selling their 901 here on taperssection, but I could be wrong. do you know of one for sale right now? just curious...
other considerations besides the sound of the unit, is how you'll be using it. you say that you're planning to use it as a DAC. why not also use it as your system pre-amp? (I'm assuming, that you're using this not as a headphone amp, as it was originally intended). Do you have a seperate pre that you're planning to use? The only outputs on the 901 are stereo 1/4" outputs. When I'm not using my headphones, I have a custom right-angle 1/4" to left/right RCA connectors. This is a silver cable made by leegeddy, and it works great. I then plug the RCA's into my amp and I'm good to go. you'll probably need a similar custom cable as well. just something else to think about.