If you want to continue pushing the S1 you need to take a look at independent X and Y accels and speeds. Slinging the heavy bed is the limiting factor in speed and accel
I've managed to get to ~12m with 250mms@3k on Y and 450mms@10k on X.
You just need to download piezos limited_cartesian.py and put it in your kinematics folder.
Then you can easily switch between by changing the kinematics option in your cfg.
I wanted to do linear rails as well but decided against it and put the money towards a VzBot and my DIY build.