If you are going with straight pipes, everyone is going to hate you because of how loud they are both inside and outside, dont expect to have to many conversations in with anyone in there ever, and after a while they just dont sound good and get annoying.
If it were me, ditch the flowmaster, pick up a good muffler magnaflow/borla and snag a cutout. Cutouts run about $100 shipped to your door for the racelands however you can get some good deals every now and then and snag them for around $80 if your lucky.
Cutouts/straight pipes wont give you a deep sound though, they will make it louder and drop the tone a little but not to what you would think. Straight pipes will also give it a raspy sound which sounds like **** IMO.
You can give it a try, see how you like it, real test is to take it for a drive, windows up and try to talk to someone in the passenger seat at highway speeds. If you like it and the loss of lowend performance keep it like that otherwise get a high flow muffler and call it a day. The XR1 that I have in mine is a straight through design, basically looks like a straight pipe, but it cleans up the raspyness to give you a good crisp sound.