Sounds lie you have the plan figured out pretty well..
I ended up getting my Cable track from McMaster Carr.
Here is a link to my build using everything you are except I am only going 3x4 in size. My gantry also is from RON, great guy to deal with. Also my electronics all from Tom at CandCNC.
http://www.cnczone.com/forums/showthread.php?t=110827 (New Precision Plasma Build 3x4)
Here is some info on my Cable track and for hole spacing on Precision Plasma's rail
Also for those using the presicion plasma gantry kit( non bolt together..)
Hole spacing on the rails is 3.15 or 80mm total holes for the 3x4 kit is 15 per rail.
Hole diameter .35
Also thank you to unixadm for giving me the Part numbers he used for the Cable track
I ordered 2-6 foot pcs and will make them fit my use.
1 4409T513 2 Each Open Hinged Cable And Hose Carrier, 0.98"h X 1.50"w Interior Size,2.17"bend Radius,6'l
2 4556T562 2 Pairs Mounting Bracket For Cable And Hose Carrier, Open, For 0.98"h X 1.50"w