I know that there is a push for the Magnaflow exhaust headre, but does anyone have any advice for a nice sounding exhaust system?

 

This is really going to depend on the sound you're going for. I did a muffler delete to my 2013 justa and I think it sounds pretty good but there is a bit of drone that I'm hoping to eliminate. As for an actual replacement exhaust kit, I think the VIP exhaust (http://www.vipcustomparts.com/vcp%20exhaust%20page.htm, about half way down the page) sounds really great. There are videos on Youtube to hear what it sounds like in action and it's got a killer sounding purr. If you're going for something a bit more aggressive and in your face, that Magnaflow you referenced seems to be the most commonly used system. That's just my $.02 though. Hope this helps

 

I did a muffler delete also, sounds much better than stock. A year later I put the magnaflow header on and it sounds much deeper and pops a little on downshifts etc. Just a couple weeks ago I taped up the holes on the intake silencer and it is perfect. No intake drone, and pops on let offs/downshifts but not too excessive.