RAID10 over 6 devices

I’ve been struggling to find the best layout for my 6 drive RAID10 device: I settled for near with 2 copies, and a 1M chunksize. As far as I understand this I get the r/w speed equivalent to RAID0 with this. It means that each block has two copies, which are striped across 2 drives. So you get the RAID0 speed, with the redundancy of RAID1. Plus since this is kernel RAID10, it’s a lot easier to create and more flexible than a mirror of raid0 devices.
mdadm --create /dev/md1 --chunk=1024 --level=raid10 --layout=f2 --raid-devices=6 /dev/sd[defghi]1

So far the speed seems to be OK. Nothing at all spectacular though. At the moment I think my limitation is that I am running a 64bit PCI-X u320 card in a 32bit PCI slot since my motherboard only has these…. I need to get myself a PCI-X dual socket 604 motherboard. Trouble is these are quite expensive…..! In my quest to silence the machine I replaced the fan in my Graphics card with a quieter one. Unfortunately whilst doing so I knocked of a small component. The card works fine except that I get visual aretefacts on any hw accelerated graphics now. I’ve alwasy steered away from upgrading my motherboard due to the fact I would need to also buy a new GPU to go with PCI-E slots. But if this is now damaged perhaps I should splurge out. Hmmm.