The other thing to consider is that your stock exhaust is one piece - the mufflers are welded to the headpipes. Older 650s used separate mufflers and headpipes. If you got older headpipes, you would need new (or at least different) mufflers anyway. So, a complete exhaust replacement (mufflers and headpipes) is the best option. If you compare prices to other bikes, you'll find that 650 exhaust systems are really quite reasonably priced. You can usually do a complete system for not much more than $300.