one twentyeth of the sysyems theoretical limitjulian, also here we have to face the relations.
you can't compare RAM usage for arguing loading times, because the footprint of a loaded sample header with ViennaInstruments is significantly smaller than with any other app, so the number of loaded samples is much higher (i'd say 2.5 times average) - this samples have to be read from a harddisk.
harddisks can still deliver just ~30 MB/s random read, if you have a very fast drive (10.000 rpm, NCQ) possibly 40 MB/s ... this affects the theoretical limit. of course your PCI-bus can deliver ~250 MB/s to memory or processor in best case - but when does such a case really occur?
and remember: only a CRAY can run an endless loop in just three seconds.