The safest bet - Rush or Vance & Hines. Many swear by Jackpot on this site (and other sites as well). You need to determine the releative sound you are looking for and then go from there.

 

I'm getting old, just want a nice sound but don't want to have the guys behind me tell me to go to the back of the group! I do like a lot of others, I see a set on a bike and ask them to fire it up.