Hey John! The .net names are a harder sell because they're not nearly as popular as .com. As such, your keywords need to be much stronger. This gives you a much wider base of potential end users, and thus a greater chance that buying a .net will be an upgrade for someone (or at least desirable).
The only one you listed that has some potential is CanoeStore. Ideally, you'd want to find online canoe dealers (something like these guys:
http://www.completepaddler.ca/site-content/shipping-info.html), who have an interest in appealing to more than their regional base. Of course, you could try any major outdoors store, and you may get lucky. Just keep your price reasonable.
The others aren't too good. Even in .com they would be iffy. DIYstore could be okay without "the", but finding end users could be tough. And ThreeDprints just doesn't work because people don't write 3D that way. Make sure you don't overthink things when you're buying names. Two word domains will have the most value when they sound great, have commercial appeal, and look the way they should.
And 6india... a Google search didn't reveal much for this one. Does it mean anything? It reminds me of one of the first .com names I registered: Wide3. I look at that one now and think: "Huh???"
