The USPTO site is probably one of my best tools for even deciding whether on not to purchase a domain. For instance, if it appears that a name I'm looking to buy may have some issues I'll stay clear. However, with DataCubeโข i believe it can be trademarked for the purpose of buying selling domains.
Moving on....the answer to your question about whether or not you should TM all your brandable names before trying to sell them is a big fat NO! Take BrandSailโข for example, while I might consider it a brandable name, I wouldn't trademark it "unless" I owned it and ran my business as BrandSail. Why?...because it simply adds value to the name and my credibility.
Finally, without a plan to outbound market your name, or at least have someone do it for you, I wouldn't consider it......piss'n in the wind is not my swag
ps. thanks for posting that USPTO link since my membership won't allow me to post links