Needed, consistant speed from control/motors or both???

I have this controller(site link below.
http://www.stepper3.com/31.htm

With these three stepper motors.
http://cgi.ebay.com/ws/eBayISAPI.dll?
ViewItem&item=2580852193&category=42920&rd=1#ebayphotohosting

I'm powered with a typical XT PSU.
Motors are rated for 6v. and with two poles I'm hooked in at 12v for
each motor -w- power resistors on the + legs.

I'm using Kcam4.0

I've been told I should reverse my connections and replace the two
resistors on the 2 +legs and place resistors on the 4 -legs???

Or should I be thinking about completely removing the + legs from the
board and have them powered by each their own power supply?

I'm reluctantly thinking about other controllers and motors if need
be, But I was initially very impressed with the combination as
assembled above. But I have been lead to believe It can do better.

If I set the software to run the motors any faster than 7-IPM, they
start to stutter. But for most applications 7-IPM is pretty slow.

TIA
for any suggestions
Peace
and Merry Christmas.

Neil