Mining on a low powered NAS machine

Hi all,

This is probably an odd question and feel free to call it a dumb idea!
I would like people's opinions about whether it would be worthwhile running some sort of mining program on my NAS machine.

The machine is an HP Prolient Microserver N40L and is used as a home server (DLNA, CIFS, etc.). It is powered on 24 hours a day and spends 99% of its time totally idle. Obviously it is not going to be a big money maker due to its measly 1.4GHz CPU, and I know CPU mining hasn't been worthwhile for some time due to the power it consumes. However, I wondered if the power usage could be offset by the fact that the machine will be running anyway, with or without mining, so will already be using power. Is the extra power consumption that mining causes enough to make it pointless (or even costly)?
Finally, if it really isn't sensible to do CPU mining, would it be any better if I installed a low power GPU? The machine does have a free PCIe2 x16 slot, so that could be an option.

Essentially, my question is: Is CPU or GPU mining pointless on this very low powered system, even when you take into account the fact that the machine will be powered up and using power anyway?

Thanks in advance for any replies!

Matt