A CyberstormPPC??? why? the PPC is almost unused. A 060 is much more important than the PPC chip.
If he is interested in demos and AGA stuff an A1200+060 would be enough (but not a tower one since these are big and ugly)
If he wants some expansion an A4000+Cyberstorm MKII will be nice.
I wouldn't waste my money with a PPC accelerator. You can get a MKII/060 with that money and if you really want PPC you can get a second hand Pegasos and crush any A4000 in performance.
