You dont have quite enough RAM - a 1208 ought to do it, but I'd recommend going for a 1230 (or even a 1240 if you can afford it) with as much RAM as you can afford . 8MB should be enough for most things, but if you wanna go online get at least 16MB if you can.
the 68030 would be a minimum of 25 MHz (get an FPU - it'll help with JPGs) which is nearly double the speed of the 68020 in your miggy.
I speak from experience here - I have a Towered 1200 with OS3.9: my accelerator is a Turbo1230Lite which will only take the 8MB its got - a bit cramped if I wanna check me mail and read the news !
summary: at least a 68030, at least 16MB RAM, try for something with an FPU.
you may need to beef up your PSU - definitely if you get an 040.
