The older RCEXL ignitions were for 4.8 volts, not to exceed 6 volts. I believe the newer ones are 4.8 to 8.4 volts, allowing you to use a 2 cell Lipoly battery for ignition if you like. Check with your supplier to be sure. Time them at 28 degrees, and the timing automatically retards for starting and idling. They really do work very well.
Those two Hobby King units you mentioned are known for being problematic, and it is no wonder that you are disillusioned with electronic ignition after using them. You'll really like the RCXP or RCEXL ignitions.
AV8TOR