The thing to take into account on the older Amigas is that they have an HD limitation of 4GB. You can stick a larger HD into them but they won't (as standard) be able to see or use more than the first 4GB.

But you can get third party file systems to then be able to use the rest of a larger disk. Or even better, with an Amiga A1200 if you upgraded to Workbench 3.9 it can use larger HDs as standard.

If you are thinking about adding an HD to an A1200 then the UK store Amiga Kit have lots of products you may be interested in.

Here is a 40GB HD for the A1200 with WB 3.5 pre-installed.

http://amigakit.leamancomputing.com/...roducts_id=175

They also have reconditioned A1200's if you don't currently have one and were interested in getting one.