For small companies,The best price/performance is iEnsemble form FlashlineVive 4 and 8 analogue ports.
H323 compatible and works fine with all others “Big” vendors. Voice qualiti is same as you can have for 10xUSD. Equipment include GW+GK+PABX functions, and for afforidable price you can have Billing solution (prepai and postpaid).
Good luck for startup