I've tried running SN Pro 6 on an iMac G5 1GB RAM with 128MB X600 Pro, definitely need more RAM for that. Graphics wise is just ok, but never tried for heavy details.
Also tried SN Pro Plus 5 a MacBook Pro 2GB RAM with 128MB X1600, and an iMac 24" 1GB RAM with 128MB nVidia GF7300. Works fine but starts to take a heavy toll on the graphics when more detailed background stars are being displayed.
Hope this will help you gauge the performance of SNP on your MacBook.