If you are happy with the way it drives and performs.... leave it alone.
What is the fascination with 6500rpm? It's just a number.
Would you be happier making the same HP and TQ at 500 more rpm than you do now? If so, you'll need more gear and you will just be tougher on your parts, especially valvetrain.
On the dyno chart peak power is about 20 mph less then where power takes a down turn, that's a lot more than 500 rpms. When I calculated rpm from peak hp and the torque at that speed it put peak hp just under 5,000 rpms.