Generally speaking, the latest version of stratux apparently has reduced the power requirement to keep the pi happy. What version of the stratux image are you using? Version 0.4r4 is the latest (as of yesterday).
Another possible issue is the quality of the USB power cable. You might try changing to another USB cable and see if it will work on the original power supply.
I've been able to run the pi with two ADSB dongles off of a UBS power source at less than 2 amps without any issues.
Hope this helps.