Regards helmets, the most important thing is to try before you buy. You have to make sure it fits your scone properly. No point buying something online to save a few bucks and finding out that it's too tight and gives you headaches or that it's too loose and flops down over your eyes.
Stick to the reputable brands, of which there are many (protech, netti, fox, POC, TLD, Bell, etc) and toss it if you crash and hit your head.
Make sure that you really need the full face in the fist place. I'll check those links later to see what you're riding because the kind of stuff your bike is designed for is borderline as to what kind of lid you'd get and you DONT want to be climbing hills with a full face on.