If you are trying to run with only 1 video card, as in no GUI card, you should go with one of the modified GTX470 cards. This will be much faster then the Q4000.
If you really need the high quality, realtime red decoding that is. Regardless without a dedicated GUI card yo may not get realtime anything. If you are working with R3d and need realtime playback I suggest this config...
Then for storage get one of the mod kits that lets you take the two internal SATA ports and make eSATA ports from them. This will give you 2-channels of eSATA ports each capable of doing up to 100mb/sec. You could then connect 2 external RAID-5/6 units... one to each port. This would give you a playback RAID and a RECORD RAID. For working with RED footage and ProRes or DNX renders this will work great. It would also give you reasonable performance for rendering 2k or HD DPX file outputs.
SAS is great, but there just are not enough PCI-e slots to do what you want to do, without using a CUBIX chassis.