Short Answer: keep it at 0 degrees and set the high pass at 80hz.
Long Answer:
The phase control is basically to help your subwoofer blend better with your main speakers. Try experimenting with the different phase degrees, if there are no audible improvements then keep it at 0. As a speaker makes sound, it travels back and forth. Adjusting phase on a sub allows it to move back and forth similar to your mains therefore allowing it to integrate more smoothly. It depends on where you put it and the the acoustics of the room. You'll be able to tell what would sound better if you try the different settings though.
Most people keep the pass at 80hz. It depends on what kind of speakers you have. Since you have that sub, I'm guessing you have some pretty nice speakers also. If your speakers can produce some of the lower frequencies (ex. <40 to 80hz), then keep it at 80 or maybe lower if you can. If they cannot, go for 100hz. For example, the speakers I built can reach down to 80hz, but can't really go any lower without hurting themselves. So I had to set the crossover around 90. That way, the speakers would stop around 90hz and then my subs would take over from 90hz and lower. The bad thing is that when you go for a higher pass like 120hz or something, then it will be easy to localize where the bass is coming from. You want the bass to encompass you, not just get you from one side.
