This comparison is based off memory of the Bolder cable, I do not have it anymore.
HGA:
Source - Pana 570
amp - Super Mini V3, META42 (AD823/EL2001/220uf Cerafines/2x9V)
headphones - Senn MX500, Beyer DT250-250
Bolder:
source - same
amp - CHA-47 (470uf/2x9V), ETA42 (AD8610/EL2001/470uf Cerafines/2x9V)
headphones - Senn HD600, Beyer DT250-80
Build quality goes to the Bolder, it's a monster, but there's no flexibility, it's unusable in a portable bag. It's discontinued but you can build it or find someone else to, just get Canare F-12 plugs and use jon risch (single belden 89259) recipie. There's all kinds of information on it.
Prior to 100 hours of burn in, both cables have edge and glare, not good, since all portable players suck. Both have good transparency, they pick up detail pretty well. The HGA has more extention, but isn't as refined as the Bolder. It's strength is in clarity, all the notes are crisp, this is especially evident in the treble. The bolder has a softer timbre, although it seemed to have allowed texture through better. Tonally, both are relatively neutral, with the Bolder leaning on the warm side (slightly more midrange presense). The Bolder has more bass authority, but doesnt sound as controlled as the HGA. I'd say the HGA has better rhytm and timing (faster attack and extended decay), but overall the sound isn't as coherent as the Bolder.
The Markertek and Kimber aren't even in the same league.
I don't think much else need to be said, I tried to explain the differences in an easy way to understand. I like the HGA very much, now I'd like to try a Silver Lace version which I suspect will match the Bolders refinement and improve on the soundstage.