Use pete's cdr plugin, pick async prefetching, enable the 4megabytes cache. This should allow faster readaheads and keep more data cached (so as to not needing rereading from cd).
Any difference?
If its unbearably slow, you could rip the disc into a disc image, should be -much- faster. IF youre reading from a CD, its in fact even normal for loading screens to be 'slow' (compared to using an ISO).