What are you planning to run? a rock band?
If so, I would suggest hiring a pro sound guy that is all set up to do the job...
For a system of this size it is really the only way to go...
Over the years, I've played in many rock bands around the country in siminal sized rooms... Here is what we used for a typical venue of this size...
2 JBL 18" Subs per side (each cab loaded with 2 JBL 18's) for a total of 8 JBL 18" speaker for bottom end
2 JBL Hi-Packs per side (each cab loaded with either 15's or 12's) for a total of 8 speakers for mids
2 JBL Horns per side for a total of 4 horns for high's
4-5 monitors with monitor board (w/ 2 stereo poweramps.. QSC, Crown, or Crest)
6 QSC, Crown, or Crest amps for the mains
a 3-way mono crossover.
A 24 or 32 channel FOH console (snakes and cables)
Outboard effects and eq's (6 stereo eq's)for mains and monitors... a few compressors....
Perhaps some stage lighting (NSI or ETA)
And last but not least: The skill to hook all this stuff up and run it
Shred