[ajj]

"My main motivation is to produce an original piece of work"

In that case, I suggest working on it right now, before a PhD. You can start doing a heavy literature review on a focused topic, and try to improve the state of the art by however small you can. The standards for publication are much lower than what many people outside academia believe.

You can do this and even get a publication without an advisor (may be not at a premier venue but a decent one nonetheless). That gives a great sense of accomplishment.

If you want to continue, the work will surely help you in your PhD (won't be wasted time). If you don't like it, you can move on to other things (and it won't feel like giving up on a long commitment).

The reason I say this: the beginning of a PhD is probably the hardest time to see results, and keep you motivated. So starting small would be helpful. Once you believe you need larger goals and are not satisfied by the small accomplishments, you can go for the long haul!