Slip-ons are NOT a bad idea. Most head pipes out are great for more flow then most will use. You would have to do some SERIOUS mods to need a new head pipe on your Z. My favorite is the Pro Circuit T-4. It has a great fit and holds up great. HMF makes a cheaper nock-off that works fine and they have some color options. You'll hear about disk systems I'm sure too but I wouldn't touch them. There is some serious science involved in a head pipe more than the silencer. If you need more info I could get it for you. Good luck.
'02 Honda 416ex - A seasoned blend of 11 herbs and spices
'04 Honda Recon - The yard machine and snow plow
'88 Honda CR250R - Another chapter in my torrid all terrain affair