Hi there.
Sorry for the late reply.

Stepmores seem quite honest in their prices, Not sure why $115 in shipping though as I was only charged $15!
Speak to a gentlman called Eric (tell him I put you onto him please)
The Steel sink/Tub if you haggle you can get for free, I did.

The Z axis I would leave be, More travel = more flex and only get the 75mm IF YOU NEED IT.

I think the weakest point of the machine is the Y rails, If you can afford the extra, upgrade to supported rails (ignore anything he pawns onto you, just get them)

As for electronics, i am not too clued up on this sorry, I have no idea if they are 23's But I do know the Y axis motor is twice the size of the other 2?

Thanks

Craig