If you want to get rid of rasp, I would suggest starting at the back (muffler). What i mean by this is that you put back in your resonators, leave in the oem headers, and put in an aftermarket exhaust. See what you think of the sound and go from there. If, after doing so, you want more volume, throw in headers while leaving in the resonators.
As for an exhaust, TSE3 would make for a great tone