The way you have it connected is probably the best. The other way would be what's called 'half coil' which, as the name suggests, only uses two out of the 4 coils in the motor. You'd then use the center white/yellow wires and BL / R. That, I think, would get the motors going faster - but with much less torque since the magnetic field is smaller due to using less coils. If I recall correctly the manual for the stepper drivers I use explains it:

http://www.slidesandballscrews.com/p...ml?cPath=44_97

If not google is your friend.

Before you were using 3.5 amps, now 3 amps so since power lost is I^2*R, that's 3^2/3.5^2 = 73% of the heat you had before.