I have 3 of Mech's SCSI CF Card readers, 2 are in A4000T's and one in a A2500HD; this the best choice for what you want. It a great choice to use a CF card as a solid state drive, for backups in the GB range, for quiet computing, and to transfer files; I use mine to boot into a completely different OS's -- 1.3 up to 3.9 by just plugging in a different card. OS 4.1 has some issues that may be CF card related.
As an aside, you can still pick up IDE solutions in the $$$ USD range, but forget about USB solutions; the only buyable one is for use in Elbox's Mediator, and although you can get a hacked USB card (~$, vs Elbox's $$), the Mediator will set you back $$$ USD. If you run OS 4.1 on your A3000, you are basically SOL, unless you are very lucky and have a lot to spend.
