Rabel

If you just want to write your notes on it. Maybe look at a 2nd gen surface laptop (I know it is only 13 inch) but it has a really nice keyboard. If you want to game on it too, the Asus Vivobook K571GT-EB76 is a Bang for your buck at Amazon right now. If you only want battery life the DEll Latitude 14 7400 has with more than 13 hours and is the best on the market (an i5 version with 16gb is under $1000)

Well, there's software motherboard RAID, and then software RAID (ZFS, BTRFS, etc). ZFS is quite fast as it runs as the OS / directly controls drives. 
 
But yeah, I don't know of a sas card with that many ports onboard. Is there any reason why you can't use a SAS expander card? The cost of a SAS expander would be much lower than a RAID card with four internal SAS ports. 
 
What kind of setup are you running? (number of drives / type of drives)

You're mixing up motherboard RAID vs true software RAID. ZFS is an actual filesystem that runs in Linux that controls the drives. 
 
But yeah, why not get a RAID card with two or four SAS ports, then get a SAS expander to expand out to how many SAS ports you need? You won't be hitting a bottleneck with hard drives (keep in mind SAS2 is four 6Gb/s lanes per port)...or 12Gb/s per lane if SAS3. Most RAID cards are typically able to handle 128+ drives with expanders

Technically, it will work with PCIe x4. Physically, it won't fit in the slot so it won't work.

¯\_(ツ)_/¯

who came to that idea?