The Command panel and any Honeywell Six sensors would need to be replaced. The sensors are unfortunately not compatible with any other Alarm.com compatible system.
The cameras can be reused, they must be deleted from the current account or the current account must be deleted first before they can be registered to an Alarm.com account through another provider like Surety. Cameras can only be registered to one account at a time.
The lowest cost alternative would be the 319.5Mhz IQ Hub here and IQ 319.5Mhz Sensors.
If you go with the 319.5Mhz IQ Panel 4 instead you could use both IQ sensors and PowerG sensors. PowerG offers some significant benefits such as much farther range, adaptive battery usage, FHSS signaling.
If you want PowerG but the lowest cost panel, you could go with the PowerG version of the IQ Hub. It would only support PowerG sensors.