So is it actually possible to get anything out of bitcoin if you're stuck with relatively low end hardware?
Bitcoin has a lot more to offer than just mining.
"with relatively low end hardware" you are only going to mine at a loss, so if you're *only* after money, mining probably isn't the route for you.
On an unrelated note, wouldn't it be possible for a corporation with enough computing power to completely take over the market and get all the blocks all the time?
Short answer: Yes, it's possible. However the bitcoin network dwarfs any current "supercomputer", and it would take quite an effort, and a lot of money to take over completely. Remember - if an entity was to match the current capacity, they would still only have half the network. If they doubled it, they would still only have 80%, and so on, tending to 100%.
Would bitcoin be used in its current form if one entity had exceeded 50% of the hashpower? Probably not. So the taking over entity would be spending more & more, getting closer & closer to total domination of something worth less & less. You would need a very compelling reason to set out on this path!