eSATA RAID 0 arrays can saturate the SATA bus.
Yes, they can.
I did this with 4 eSATA drives in a G5 with Apple's software RAID a couple of years ago. I only did it as a test, and I was surprised that it worked, but here goes:
disc 1 and disc 2=raid 0 array #1
disc 3 and disc 4=raid 0 array #2
raid array 1 and raid array 2=raid 0 array #3.
array #3 was blazing fast. seems like a trick, right? I was surprised that Disk Utility allowed me to make that 3rd array from the other two. Turns out it will make any combination of arrays.
Of course, it was also 16x more likely to suffer an unrecoverable hardware failure, so I took it apart and made two RAID 1 arrays instead.
I didn't do any official tests or anything, but I can tell you that I did duplicate a 4 GB file on the array in just under 20 seconds.
the rough math puts that at about 200MB/sec. Considering that this wasn't using a hardware RAID card, which is certainly faster, I'd say triple the FW800 bandwidth isn't impossible currently with eSATA.
I look forward to the day that you can affordably create a reliable array with those kinds of speeds and large capacities, too.