Distortion can be caused by your settings being too high which overloads the internal preamp on your recorder, but it can also be caused by overloading the mics. If you check the specs for this mic, the standard sensitivity version of this mic is rated only up to 105db which isn't all that high for loud rock music. I can't really tell you what the bass volume goes up to during a typical loud rock show, but the specs on the low sensitivity versions of this mic go up to 120db, which would help your cause. So, I agree with acidjack that would be a potential solution to your problem. That said, 120db isn't the greatest upper range either...I typically like my mics to be able to go up to the 135db range, but I'm not sure this is available in a mic that's <$100 (not saying it isn't, I just don't know).
Give SP a call and see if they can mod your mics to match the specs for the low sensitivity version, or tell them specifically what you want to record and they should be able to recommend a reasonable solution to you.