EXS 24 Logic Sampler Users Group

hi,
i recently bought a portable setup (icebook500 with emi2|6, mt4 and logic)
and wonder if the exs24 is worth its price for my system? the icebook has a
G3@500 and the bus is at 66mhz. i simply cant reach 3 ptverbs with this
(only 2 and a few other less demanding plugins), otherwise the system works
great. but how will it be with exs24?

i lent my emi2|6 to a friend with a 500G4 and he got no noticeable latency
playing an exs24 piano (when emi's ASIO was in the fastest setting 6ms, but
i get hiccups at that. not under the other two). but then again he only
tried one instrument at a time (and he has a G4)

any ibook experience here? how many exs24 should i be able to simultaneously
play?
i have the akai advanced orchestra in akai, and plan to buy a firewire HD
for storing audio files and the exs24 samples. will it be better to have
disk streaming than ram streaming with an icebook?

last one. is logic 5 'slower' than 4.8.1? i dont know whether i should
upgrade
thanx, greetings from Mallorca