6x 600 GB drives, including 1 hot spare. 5x 600 GB = 3 TB total storage, so you can spare one drive's worth of capacity, but not two. So none of the multiple physical array options will provide enough storage, even if they share a hot spare, as they'd each use at least one disk for mirror/parity. give you 1.8 TB at best.
Now, there's an option with HP array controllers that might help you if Dell do something similar (all my experience is with HP servers, but Dell are usually not too far behind on the technology front). It lets you have multiple logical arrays with different RAID levels in one physical array, I'll try to explain.
HP will let you configure a physical array with 5 drives and a hot spare, but not specify a RAID level for the physical array. You can then split it into logical arrays with specified RAID levels and arbitrary sizes. So you could specify a RAID 1 and a RAID 5 logical array, and it would use part of each drive for the RAID 1 and part of each drive for the RAID 5. Performance is distributed between the two arrays in proportion to the native performance of that RAID level.
So, if the RAID 5 logical array is idle, the RAID 1 logical array will get all the performance of 5 drives. When the RAID 1 logical array is idle, the RAID 5 logical array will get all the performance of 5 drives. When both logical drives are equally active, then performance will be roughly equivalent to a 2 drive RAID 1 and a 3 drive RAID 5, but in practice it should be better as long as both logical arrays aren't constantly saturated with reads and writes.
It's comparable to the way SANs virtualise storage, where you get RAID 1, 10 or 5 equivalent performance and redundancy for each LUN, but spread across maybe 60 disks that are shared with many other LUNs.
Advantages - you can specify logical arrays that aren't a multiple of the drive size, without wasting space. For example a 250 GB RAID 10 (which will use 500 GB of your total storage, 100 GB per disk) and a 2 TB RAID 5 array (which will use 2.5 TB of your total storage, 500 GB per disk).
When one array is utilised much more than the other, it will get more drives worth of performance.
For logical arrays with parity, you lose proportionally less space because it's spread across more drives.
Disadvantages - if you lose one drive, all logical arrays get degraded.
If both logical arrays are heavily used at the same time, then the perfomance advantage is reduced - it could even be a slight overhead v.s. two separate physical arrays. But that's usually worthwhile for the added flexibility and capacity.
Sorry if I've just given everyone a headache, it took me a while to get my own head round it while writing this!