Need solution for RAID from old Mac
You're using Apple's RAID which means you need a device which just hosts the discs and then your new laptop will see them and use the existing RAID structure. This rules out NAS.

AS these are existing RAID arrays you can't simple merge them together to create a single new RAID. At least, you can't while keeping the data on them.

Essentially, in one device you just need a 6+ array of the disks to be presented as individual drives to the new machine, which will then pull them together into the RAID.

You could also use any number of single, double, quad enclosures too, but, I'm assuming you want a single device.

A device like this: http://www.tigerdirect.com/applications/category/category_slc.asp?CatId=4274&amp;Nav=|c:4269|&amp;Sort=3&amp;Recs=10 would do it in one.

Put the drives in, connect to your new laptop and start using RAID.

If you've happy to lose a drive, the Drobo's are pretty neat. Not the fastest, but very usable, and generally easier than normal RAID. It's the easier, most it-just-works storage solution.

If you want to get geeky, then ZFS is the best solution: https://openzfsonosx.org However, it's still essentially beta (despite being very stable), and it's not an officially support Apple filesystem. It'll give you a nice range of options to use your disks with. Again - this requires a rebuild, unless you were really cunning and broke the RAIDs up, kept the data on one half, at least the mirrored one, started a new ZFS and then copied the data over and created two mirrored vdevs in a pool together. You'd need a spare 2Gb drive in the meantime.