DS 1650 Flex Force PRO Top
, this is the cheapest, and its a full upper protector. Doesn't seem to go into detail about the back protection abilities though)
I've got this jacket armour and it's pretty damn good. I actually don't think there's any hard shell armour on the spine, only approx 10mm padding. I've tumbled onto my back lots with it and it feels great, like Lonerider said nothing will save your back if you taco on a rail or knuckle! lol
I ride quite aggressively, and sometimes take some nasty falls, and so far the armour has saved me from getting seriously hurt more than a few times.