Some modern ATX supplies aren't even coming out with a -5 V rail any more which means a 7905 needs to be connected to the adapter cable with a couple of capacitors.
I personally run a 430W Thermaltake PSU in my A2000 which is;
A2000 base board
CDROM ( SCSI )
2 x Acard Scsi ---> IDE
2 x 4Gb CF cards
GVP '030 Combo with 16 Mb
I think the problem with power supplies now is that it can be hard to find a reputable supplier / manufacturer that will continue to make a product for more than 5 minutes before it's superseded. It still remains a better option to make the adapter cables like Amigamaniac used to ( still does ? ) or Amigakit, but then you still have to specify whether your ATX supply has the -5 V rail.