The analog models have the square brain and the digital ones are rectangular. The multichannel digital brains have the most versatility in timing and will therefore create the best power. The analog brains are ok for the money but they require special plugs to set the timing and no one sells them anymore. The analog brains are also notorious for dying. The single channel brains are pretty good IMO and you set the timing with dip switches on the back of the brain like the multichannel but their timing curves aren't as customizable.
I agree with Matt_E on $300 max for an analog system. The flywheel, pickup, and pickup plate are worth about $200 of that $300 too.
