I can't wouch for OS 3.5, but an Amiga 1200 on OS 3.0/3.1 with:
* Harddrive/CFcard
* WHDload
* 4-8MB RAM expansion (doesn't even need better CPU)
really works great for most gaming.
You can either WHDload patch your copy of the games or there are actually pre-patched ones in zip archives to get (just copy to 1200 HD and you're good to go).
I know I've played both SotB 1 and 3 on my Amiga already so I reckon 2 should be avaliable.