The amount of difference in power gain from an X pipe as opposed to an H pipe is negligible , unless you are up in the 5-600 horse range. Then the X might net 7-10 h orses.
Run the H. They are far cheaper, I have the Flowmaster H pipe mandrel bent system on my ride. It was like 360 bucks from summit. Worked out nice.
I would order it without mufflers if I did it again as the flowmasters are a bit droney at a certain RPM. I think the magnaflows are a better sound...like the 40 series.Or even the 40 series deltas.
My buddy was standing around when I drove by and he said it sounded real good with the flowmasters on it. And it sounds good at an idle and when revving in the shop, just wanted to mention the flow masters do have a little drone at certain RPMs and may or may not on your car.