circuit design: wheatstone bridge gaz sensor design enhancement

I need you to improve the design of attached gaz sensor. The order of priorities are: - as low power consumption as possible as it's running on batteries. - Today I use INA333 and OPA643N amplifiers. I'm not sure they are all needed. - reduce the cost but it's not the priority You can use other Amplifiers but they need to be at least as good in terms of performance and of course lower cost. When I mean performance I talk about power consumption and available bandwidth. The system requires at least 30khz of bandwidth