I highly recommend looking for a bowl-shaped keyboard as the second priority after split. Kinesis advantage is popular, and similarly priced to the keyboard.io. There are also maltrons, if you're willing to shell out a little extra dough. There was also a project to make a bowl-shaped split keyboard you could 3d-print at home. I can't remember the name.

I was also very excited about the moonrim, a project that portended to go a step further and change the hands' orientation, so they would face inward instead of down. Sadly, it ended up not taking off.