Dan just for thoughts, I've been using ARO ballasts on mine and I really cant say anything negative about them because I haven't judged them against anything else. Their just what I picked up at the time of setting up the system.
I'm running two of them with XM 20ks
Below is the description taken off from Hellolights website.
The ARO electronic ballast is nice looking and best of all, its easy to set up. It will run any 250 watt lamp and comes with a 3 year warranty.
* UL approved
* 250W Electronic Ballast: Energy Saving - up to 25%
* Model #LN-250-02
* Extended Lamp Life - up to 25%
* Consistent Lamp Color
* Uniform Lumen Output
* Reduced Lamp Flicker
* Cool, Silent Operation
* Long Ballast Life
* 120VAC, 250W, 2.2Amps
* Works with all 250W lamps.
* Works with 250W HQI double ended lamps.
* One lamp ballast.
* 3 year warranty.
* Power factor >90%, Lamp Current Crest Factor < 1.8.
* 8 1/2" x 3 3/4" x 2 1/8" (LxWxH)
Just a thought, keep us updated, can't wait to see this thing up and running.
George