I have the exact same setup you have now. A couple months ago I got a loudmouth catback handed to me, so I put it on. The difference in "loudness" is plain out rediculous. If you think the flows are loud, my friend you are in for a rude awakening. I was scared to rag on it from stop lights cause it was so damn loud. And I mean LOUD! The flows are mild as hell in comparison.
SLP good: awesome at idle, great sound cruise. Half throttle 2,500 to 4,500 or so sounds good too.
SLP bad: High RPM or WOT will make you paranoid and give you a headache.
I would like to note that I am NOT bashing SLP in any way. A catted pipe would calm it down, so would the LMII's. I'm seriously considering purchasing a set of the LMII mufflers to use instead as the quality/look of the SLP catback is outstanding compared to the flows. The SLP LMI's are simply too loud and raspy for my taste when paired with an o/r h.
I hope this helps.