Well there are more factors to yield than just light. My instinct says that it will be so difficult to exhaust the heat from a HPS1000 from that space that you will actually end up shooting yourself in the foot yield-wise. In a larger space, a HPS1000 gives more yield. But the footprint to run one should be a space 5x5 feet and at least 8 feet high. You could FIT one, if you can exhaust it- but that's something you need to find out.
Have you ever grown before? The way you phrase your questions about lots and lots of yield hints that this is your first time out. In that case, you will DEFINITELY want to make absolutely sure you do not have heat problems, as they are a guaranteed path to disappointment!
Edit: How long do you plan to veg the plants before flipping them over to 12/12?