I have the Mackie C300 non-powered speakers, similar to the SRM450.  If the 350's are any way as similar as the others, then I would say you couldn't go wrong with the Mackies.  I would suggest a sub-woofer if you need to fill a space for more than 100.  I have an EV Sb121 powered sub that really adds punch to the mix.
[This message has been edited by cassp (edited 02-05-2004).]