Recommendations for a "mid-fi" digital coax cable?

Audiogon member Joemazzaglia sells Auricle Audio Design digital IC which meets all your criteria plus being wonderful performer very far above the merely mid-fi level.
I use his 1.0m length in a number of systems.
Personally, have not compared the same digital IC in both 1.0m and 1.5m length as this is a newer idea to me.
I use jitter reducers such as Genesis Digital Lens in my systems, and this may mitigate some of the claimed shorter length "shortcomings."

I'm really impressed with the analysis plus digital oval -- a little over your price but you can find them used. It trounced my previous xv2, adding (letting through) more warmth and heft without sacrificing detail. Meets your criteria nicely. I use a 2m w/ bnc-rca. The Straightwire Infolink and Wireworld Gold Starlights are also nice cables you can find used in your price range (I still use the infolink in one of my systems (xlr).

You'll hear lots of opinions regarding digital cable lengths. My experience leads me to believe that it depends on the cable. For example my (bnc-rca) one meter Tara the One sounds better than the 2m analysis plus. Then again, I haven't compared it to a 1.5m or 2m Tara. The idea is that the longer length reduces reflections in the cable that smear the signal (timing). If the price isn't that much more, I'd go for the longer piece, but I'd get a 1m better cable over a 2m lesser one.

Signal cable Silver Resolution Digital interconnect.

You don't need to spend $150 on a digital cable. Any one sold by Benchmark Media will do. You can find them from this link

http://www.benchmarkmedia.com/catalog/cables-c-44.html

The Apogee Wyde Eye would come in well under your budget and is detailed yet also smoother, more liquid and full sounding versus some of the more detailed and analytical digital interconnects I've had in my system.

transparent premium digital find 1 used very nice silver ones sound to small and bright

Stereovox XV2, which you can purchase online at gcaudio.com. Chris Somovigo's successor to the Illuminati cable. Engineered correctly and well made, works with both RCA and BNC connections. Go for 1.5M just to be safe.

The plain ol' copper Signal Cable digital coax is suprisingly good! For something like $30 and a 30 day home trial, you can't go wrong.