To run at 5kW of power you might as well consider going back to using a full H-bridge. That is the classic efficient method to obtain positive-and-negative polarity AC, at the amplitude you want.
Even if you end up keeping the boost converter, consider joining multiple interleaved boost converters. This has benefits:
(a) smoothing current ripple taken from the DC power supply,
(b) sharing the heavy current load among several components,
(c) lessens current spikes into and out of the smoothing capacitors.