Amiga hardware isn't always the same. A hard drive is not always an
Amiga hard drive.
I once bought a Quantum Daytona 2.5" hard disk from Anal-Logic
computers but it turns out that even this Amiga dealer had sold me a
drive which had technology only a PC could talk to - thus the drive
wouldn't work on PIO Mode-1 that the A1200's internal IDE header has.
Also, the A1200's PCMCIA port is Rev-1 standard whereas today's
laptops have Rev-3 or something.
Another variant is memory. Amigas won't like a lot of EDO SIMMs or
server intended memory modules - whereas you can virtually guarantee
that a zero '0' before the nanosecond rating will guarantee you a
fully compatible FPM SIMM.
I would pay a higher price for something that had been proven to work
with an Amiga (with a tech explanation) than some generic, unbranded
PC part. I would also pay a higher price for service and guarantee
from a trusted Amiga specific company.
Bare in mind with IDE cables though that the A1200's IDE header isn't
very well labelled and the cable can be inserted in the wrong way
around. This can kill hardware.
Also - the unbuffered IDE interface of the stock A1200 really should
have a short (2-4") cable.