Re: is "client power management" understood by non-Cisco cards?
What you are describing is often referred to as DTPC (Dynamic power control or Dynamic transmit power control). The following link shows the syntax for it. It only works with clients that support DTPC. This is a capability of clients that support CCX (v4 I believe). Most modern client adapters support CCX, as long as you are using their client software (such as ProSet for Intel). If you tell us what cards you have I can try to find if they support CCX and DTPC.