@moijk
Hello there =)
There are a couple of steps for the A600 to have an internal Harddrive -
Firstly the original Kickstart ROM on the first release of the A600 can not see the IDE port and the second revision of the Kickrom would only access upto 40MB.
So I would suggest you upgrade the Kickrom to Kickstart 3.1, this comes with other benefits like better disk preptools etc.
Memory
The A600 is a little low on the ground for any expansions when comparied to other Amiga's (except the CDTV/CD32 perhaps)
I would recommend upgrading the CHIP ram from 1MB to 2MB - these upgrades are quite common and some offer other features like
A real time clock,
Clock port(s)
Indivision ECS adapter
Now, to make the most use from any Amiga I would recommend WHDLoad, alas this requires a little more than 2MB IMHO to really.
With just 2MB you can use WHDLoad by removing the "pre-load" option although some games still wont be able to run.
Fast Ram is what is really needed, alas there are very few adapters to help out.
PCMCIA SRAM -
This can go-upto 4MB of extra memory, alas this can get quite expensivie, it also uses up the PCMCIA port so theres no option to use network cards, CF-PCMCIA adaters or other PCMCIA peripherals.
Accelerator
There currently exists only 3 accelerator cards for the A600 -
Apollo 630 (Viper 630) - 68030@ 33/50mzh
(Upto 32MB RAM, PCMCIA compatible)
E-Matrix 630 (T630 / Viper 630) - 40mhz
(4 or 8MB soldered to the board PCMCIA incompatible with 8MB)
Apollo 620 68020@25mhz
(upto 8mb 72pin - with 8mb conflicts with pcmcia)
*There exists the A608 project, which I am still waiting for the PCB's to turn up, I have been contacted by a Emily Wang from our PCB confirming the PCBS will be shipped tomorrow... so fingers crossed eh?
Hardisk size
Now this is upto to you, I would recommend anything upto 4GB 2.5" IDE HDD, theres quite common so relatively inexpensive, so shop around.
You could use a compact flash card as a Harddrive, but I would recommend that -
1. You buy branded media
2. You buy this from a reputable seller
Of course using compact flash as a diskdrive you will need to buy an IDE to CF adapter, SkyDivinGirl has put up a thread that links to very inexepnsive and compatible units
Hope that lot helps =)