Neofree : "Can get a powersupply for $30 on ebay" ... don´t do that !! Get yourself a brandnew ATX powersupply and use an original A4000 powersupply plug and connect those two together so you can run an A4000 with a beefy 500 Watt :-o
It looks something like this :
Amiga Stecker 6 pol. -> PC ATX Netzteil
Pin 1 (Power Good) -> Pin 8 (normalerweise grau)
Pin 2 (-12 V) -> Pin 12 (normalerweise blau)
Pin 3 (+12) -> Pin 10 (normalerweise gelb)
Pin 4 (GND) -> Pin 3, 5, 7, 13, 15,16 oder 17 (normalerweise schwarz)
Pin 5 (GND) -> Pin 3, 5, 7, 13, 15,16 oder 17 (normalerweise schwarz)
Pin 6 (+5 V) -> Pin 4, 6, 19 oder 20 (normalerweise rot)