I read that it helps with stability to run power to the floppy power connection.
What other hardware have you got running off the A600 motherboard? Because I really doubt that any instability you might have running a stock A600+CF card is anything to do with the power supply. Maybe if you had an accelerator hanging off the top of the 68000 it might, but even then it's only a possibility.
Injecting power in through the floppy connector is only something I've heard of in relation to the A1200 which can run pretty hefty accelerators and graphics boards off the trapdoor slot, requiring significantly more power than the board was originally designed to supply.
As has been suggested before, try booting it with nothing else attached and see if you get any colours or the purple Kickstart screen...
