$200-$300 (before HDDs) NAS with extra feature

I am looking to build a small NAS with an extra feature (http://www.tomshardware.com/forum/238440-50-best-distro...). Basically it will be monitoring a special folder on the local system and converting video placed inside that folder into a non-proprietary format using ffmpeg.

So far, I'm thinking of the following:

Prodigy Mini-ITX Computer Case: $75.29

ASUS C60M1-I AMD Fusion APU C-60 (1.0GHz, dual core) AMD Hudson M1 Mini ITX Motherboard/CPU Combo: $79.99

Crucial 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1066: $26.99

2x Western Digital Green 3TB Hard Drives: $159.99 each

I would also like the Hard Drives to be set up in RAID1, as they will be used for backup and media playback mostly. Would my setup be able to handle RAID1 without an external controller (my concern about the external controller is expense, as I chose this motherboard for its 6 SATA ports, which I hope to fill as my space requirements grow).

Thanks in advance