What's the correct Red Hat version?

Good morning.

We want to install MySAP ERP 2005 on Linux on a IBM xseries 346 64 bit.

I've seen that Red Hat EL 4 is certified by SAP

In this page, http://www50.sap.com/linux/platforms/index.asp, is also specified the kernel to use.

But I haven't find any other suggestions on http://service.sap.com/pam

I'm a little bit confused about the correct version: AS, ES... 4.2, 4.4, 5?

Can anyone please give me a suggestion about the correct version to choose??

Regards,

Luca