I've posted some code for controlling speed controllers with an Arduino, using bluetooth and the BlueBots app for Android, but there are a few other threads on the topic, too.
http://www.chiefdelphi.com/forums/sh...5&postcount=12
I've tested the code, and it works great with dual CIMs and an UNO R3, can't see why it couldn't be modified to run 8 motors. It also has code to check for errors in data packets, and to shut the system down if a data connection is lost.
If you need more processing power, just step up to a MEGA or DUE... just watch that the new Due processor has 3.3V I/O lines, as opposed to the 5V lines on the Uno and Mega.
Jason