What's an Amp between friends? (1 reply)

I have an ATX12V style power supplyavailable, with 6 Amp and 10 Amp rails at 12 volt rating.
I have a MK2 PCB hotbed that I plan to used, with RAMPS.

The RAMPS 1.4 page says I should have 11 Amps

I am only (1) Amp short... I mean, what's 1 Amp between friends? :S
What will happen?

If I need a different supply, how accurate must the 12 volt be?

Is an unregulated DC supply ok, or is that asking for trouble?

Thanks,

Richard