If you're only intending on playing WHDLoad games, then all you need is 4mb or 8mb Fast RAM. WHDLoad will be more than happy with that amount. I have an 020 A1200 with 8mb Fast RAM, as well as a CD32 with SX32 and 8mb Fast RAM and WHDLoad games run perfectly fine on them both!
WHDLoad doesn't take advantage of an 030 accelerators, it just needs extra Fast memory. Unless you want to use your Amiga for serious work, play a very few old 3D FPS games or 030 demos and games installed from the hard disk, then you don't really need the 030. Save some money and just get a RAM card, and let those expensive 030s be sold to the developers and other people who will get some real use from the extra CPU.