What you are asking for is known as "port muliplier" feature, which allows the visibility of multiple disk units thru a single e-sata connector.
Unfortunatly this is not (yet) managed by Intel RST software.
I have read somewhere here (from an unofficial Intel people) that maybe sometimes it will.
I dont know other driver for ICH10 capable of port multiplier.
With your Asus board e-sata was probably using an additional sata chip with this feature.
One workaround solution is to buy a PCIe 1X card with a chip known to have the feature such as Silicon Image.