Hey ,
if you want go with Apple Mac , any G4 from pci or agp 400 mhz to the MDD dual 1,25 Ghz model with Mac OS 9,2,2 ,
the MDD dual 1,25 Ghz is the last G4 with Mac OS 9,2,2 "Native" compatibility (only the model with firewire 400 ports, the "MKII" with fw 800 do not have OS9 Native)
Check last version of the Delta1010 driver available for Mac OS 9,2,2
here :
https://m-audio.com/support/drivers
Also driver for some version of Mac OSX are available ,
a bit "heavy" OS for Apple Mac G4 , but more stable than Mac OS 9,2,2 ,
if you want the max cpu power available from Apple Mac with PCI slots also some Apple G5 can be the solution ,
you can check the models with PCI slots here :
Technical specifications for the Apple Power Macintosh G5 series. Dates sold, processor type, memory info, hard drive details, estimated retail prices, and more.
everymac.com
depend from what DAW software and version you want to use ,
if the PC Windows OS based is the intention , the drivers for the Delta also are available on the M-audio web site
(same link indicated above) check about ,
for the PC hardware computer info you have to do a research about mainboard , CPU , etc... , of early - mid 2K years age .