Great price. Why don't you try it on your current engine? Your bike is so light I doubt you will experience any problems with lack of low-end performance.
I'm not runnin the MAC muffler but the head pipe is workin well on mine. Its so easy to swap out the exhaust, you could do a cool comparo test. I would do that on mine, but I can't tolerate the noise. The MAC muffler is major loud.
The steup I have pretty much attaches the stock muffler to the MAC header, in shall we say, a semi-permanent fashion. It's a royal pain in the keester to remove the muffler from the header. I take it off all in one piece. But you currently have a stock header set up with a muffler, and the MAC system including a muffler. Easy swaparoo. Switch em back & forth a few times and let us know how they compare.
That really is a great price.