Using SDIO/SPI from a SDRAM, via separate microcontroller and over to WiFi 802.11b/g, what is the expected bit rate?

Using SDIO/SPI from a SDRAM, via separate microcontroller and over to WiFi 802.11b/g, what is the expected bit rate?  In ideal conditions, user(s) can expect about actual data throughput of ½ of the WLAN PHY rate the module is connect to the AP at.