MoTeC M4 is worth around $2200 without any options.
In terms of idle quality, build quality and performance, Power FC and MoTeC are on par. The advantage that MoTeC has is that you can configure it to do more things - such as control a shift light, run traction control, wideband lambda, and in extreme cases use it to trigger and air shifted gearbox...
In my opinion, PowerFC is ideal for a street car and most weekend track cars, but for a more dedicated race car that needs laucnch control etc, etc... go for the MoTeC.
The probblem is that the M4 is designed with 4 cylinder engines in mind - it only has 4 injector and ignition outputs. For a 6 or 8 cylinder engine, you need a M48 or even metter an M800..
Cheers,
Matty