Hum,
yeah, that sounds like the best way, (through a powerflyer EIDE interface + power supply), though a bit messy if not in a tower..
(There are no drivers to drive those nice PC external cd drives, as they are...)
if you have a search around for a squirrel SCSI interface (pcmcia ) with drivers, then all you need is a external scsi cdrom... (a bare 24-speed SCSI CDROM mechanism is about £30)
I generally think a 8x speed is fine for the small file sizes of the amiga operating system...a 42x speed may actually be slower...
Try the hardware-company links here...(or
amibench)
Good luck