Holeshot's midpipe now comes in 304 Stainless Steel. The new midpipe does not have a centerstand stop on it like the older versions, but it does come with a centerstand stop bracket that you bolt onto the bike.
Yoshimura's 2G slipons also come with stainless midpipes, as do some other brands, but I don't recall who else does what as the Holeshot and Yosh are by far the most popular choices.
You don't HAVE to rejet with anyone's slipon, but you'll get a better running bike if you do.
If you're going to go with a full system, you might also want to consider the Brock/Hindle Bandit header. That's what won Fast Larry's Bandit header dyno shootout (sorry, can't find the link to the test, but ir was ~2hp up on everything else tested).