What do you use the PS3 for versus HTPC? Like what are some of the end goals you have for the whole setup? Why are your files SO huge? You'd be surprised at the quality of a nicely ripped/encoded 1.4GB movie file and even most blue-rays are under 5GB uncompressed. 8+GB seems just redonk man. Like I said I have a total of 1TB of storage and I have all seasons of Top Gear and a bunch of other tv shows, at least a hundred movies, and off-site backups of mitsystyle.com, scheides.com, etc.
Check out the WDTV or better yet ask Spazzy about it since he's around you a bit more...it's so badass for the money! All I use it for is watching um, legal copies of dvds and blue-rays I already own, and youtube (now youtube 'leanback'). It has netflix support and hulu plus as well, all in full 1080p.
http://www.wdc.com/en/products/products.aspx?id=330
I actually have the 'WD TV Live Plus' but I purchased it almost 3 years ago...I think the most basic model now does all the same stuff but is physically slightly smaller.
Don't forget that with RAID you loose some percentage of total disk space, that's the trade-off for redundancy. RAID6 is a great option but you gotta really pony up to make the investment for a bunch of similar/identical disks and upgrading is gonna just as painful down the road.