Congratulations! I have a 6700 and it is a really lovely machine. It was my introduction to the flatbed, semi-industrial machines and I am so glad I have made their acquaintance. I am sure you will use the serpentine stitch a lot. It is my go-to for snuggly, not-densely quilted treats.
A couple of thoughts:
Consider adding the AccuFeed HP foot. It is a narrower foot than the standard 9mm feet and it works with the HP stitch plate. I have this and it is fantastic for sewing on binding.
Add-on the little pedal that allows you to activate the thread cutter with your foot. They call it a “remote thread cutter switch”. Since you are already a fan of the knee lift, I think you would like being able to use your hand for other things than telling the machine to cut. I have a couple of Jukis who come with foot-pedal thread cutting standard and they have spoiled me for this feature. It really is a time saver.
I hope you enjoy creating on your new machine as much as I have.