eSATA in IDE environment

I wish to prepare for the connection of an external SATA disk (in an enclosure) via eSATA to one of the two SATA onboard hubs of my ASUS P4P800 Deluxe MB under xp-sp2. I already went through a number of forums on the topic of SATA/IDE mix and I still have doubts. Some time ago, I successfully used a SATA disk for a limited amount of time on one of the SATA hubs, but it would supersede one of the IDE channels.

I am currently running 2x IDE on primary IDE Channel, 2x optical disks on secondary IDE channel and 2x IDE on a Promise Ultra133 TX2 IDE controller.

I intend to install on the pc a simple cache containing two female eSATA hubs, each one already mounted with a cable connectable to one of the two SATA onboard hubs. I’ll be using the primary SATA hub for the external disk.

1) In the BIOS setup, should I select “P-ATA + SATA” or just plain “SATA” considering I will be running a mix ?
2) Should I plug the ribbon connector for the two optical readers onto the second hub of the Promise Ultra133 which is currently free?
3) Is there any use for the onboard RAID connectors here although I am not in a RAID environment?
4) Am I better off installing a Promise SATA300 TX2 PCI card rather than using the onboard SATA hubs?

Any comment would be greatly appreciated.