If you want to update the OS, I would stay with 3.1 unless you have accelerator in A600, which you probably don't have or get easily

3.5/9 are bit heavier and memory hungry compared to it.
Extra memory is needed if you want to do anything more "serious". There's new 8M expansion around, which sounds to work well.
http://lvd.nedopc.com/Projects/a600_8mb_2/index.htmlFor exapmle for networking 1 or 2 MB is bit too limited. You can do basic filesharing etc, but most GUI based softwares would need more memory.
PCMCIA network cards are cheap and easy way to get it connected. Wireless cards need 3.1, but cards with wires will work even on standard non expanded a600.
Prices were low about 5-8 years ago, but then they've insanely gone up

So.. it seems Amigas have been an investment rather than waste of money as PC people used to say.. and how much is their HW worth for now
