Threddersmatelot

Have just completed building my first 4wd buggy. I bought metal bearings and also a GT-tuned motor.
My ESC is a TBLE02 and I have a 4300 NIMh battery.
What are my hop-up options with regards to making it a little faster without going down the whole Lipo route?

I understand I may need to get a different ESC for a higher power motor, I'm just wondering what is the limit with regards to the gears / transmission on this model.
At what point are hop-ups to aluminium driveshaft and gears needed in relation to motor power?
Thanks for any advice.