Check EBay for the ribbon cable, I've seen them
there with 4 device connectors for about $5.00 U.S.
200 watts should be plenty, I had an PC-AT tower
case for my SCSI case on my A500 BBS machine
and had 3 Rom drives and 2 hard drives on a 150
watt PSU. I also used the PSU to run the A500 with
A570 CD rom & AmiTrix SCSI controller for the tower.
Never had a problem with power.
So go for it, it should work fine.