I know that there are some users that have a similar configuration but overall with Quads parked in the motherboard and set to 64bit mode with 16MB+ of mem - you should be fine.

So you're on the right path with using this much ram and the 64bit mode as well. Concerning the tuning aspect for the FC HBA, I would leave the FC HBA defaults unless you really know what you're doing. I was reading a forum posting with VMware, cant remember for the life of me....but, the guy stated that most of the tuning will be with the ESX server instead of the FC HBA on the Target side. Though I would enable the Write Back function for the LUN.

Concerning the kernel version I would not use the older "backup" kernel, stay with the newer kernel.