Knee armor - pick whatever you like. Go with it.
Back protector -
get a name brand item with an EU level 2 rating. There is a world of difference between the items you linked to, and something like this:
http://www.visordown.com/product-fea...tor/24572.html
http://www.spidi.com/eu/eu_en/back-p...or-motorcycle/
http://www.alpinestars.com/bionic-air-back-protector
The differences are much more than just pricing and branding. If you try a few name brand ones on, and a few of the others, you'll see what I mean. This has been discussed before, you may want to run a search:
http://www.kiwibiker.co.nz/forums/sh...back+protector
All the best with wahtever you go with - but I wouldn't (and didn't) skimp on my back protector. There is a measurable difference in force transferred in an accident between the pricy and the cheap ones. On top of that, there's comfort, durability.... better $60 than nothing but a $200 protector is much more than 3x as good as a 60$ protector. Especially when it's your back.
I think the 'racing' pressure suit you linked to is aimed at dirt/offroad. If you have a spine protector and an armored jacket, that's all the points of impact covered off much better than that $100 suit, and much more comfortable/convenient as well.
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