Also, as you listed a bunch of tube cdp's and DAC's , keep in mind this does not necessarily mean they will fix your brightness issues...products like the Benchmark fix the source of the problem, digital distortion and poor conversion instead of trying to band-aid it by putting tubes in the circuit. There are some incredible sounding tube DAC's and players, and some that could make me run screaming from the room, so don't assume they are a magic bullet.
I have always liked to try out gear for longer than a home audition would allow...that is the beauty of the Gon' if you don't like it you can often get most or all of your money back selling it, especially on popular pieces like the Benchmark, though I think lots of people decide to keep them. The Stereovox cable does offer a very noticeable difference versus a Signal Cable coax I have in my rig feeding a Benchmark, so for $75 it is a good addition IMHO.