As has been eluded to, see this not as a reason to shoehorn a home theater system into a commercial space. See it as a reason to bring what you have up to a proaudio level.
Changing all to powered speakers will probably blow the budget (at least for anything good). You haven't stated what model Passports or receiver you have. Hopefully your receiver has l/c/r preouts for use with an external amp. If so, I would get 3-4 channels of proaudio amplification, perhaps used Crown CE or XLS. These amps go for cheap, are workhorses if treated properly and can be used with a variety of setups (futureproof). Get another Passport for your center channel if you can find one. If not, get a similar sized model (horn, driver, cab) from one of the commodity manufacturers like EV, JBL, etc. Do not be afraid to go used here, but try to buy with some kind of warranty even if it's 30 day. Keep your sub as-is since it seems to serve the purpose. This should all come in under budget.