I just double checked the spec sheet and the manual for the 1050, and I don't see anything about a different power rating based on 8 ohm vs. 4 ohm. Only the 8 ohm is listed. I'd give them a call and ask, if you're really interested in knowing.
Here's their numbers:
Sales: 1-866-OUTLAWS (688-5297)
Support: 1-866-OUTLAW2 (688-5292)
If you do, why don't you post the answer here. If you're asking, there is probably a few others out there with the same question.