I'm not entirely clear on how load is spread across multiple cores, so I'm going to ask this. Assume that RAM is 8GB and GPU is sufficient.
Let's say I have a game I play, and in this game it benefits me to have multiple clients running. We'll use WoW for example. Now assume I have 8-10 accounts, and I want to have all 8-10 active at the same time.
Would a 1090t be (noticeably) better than a i5-750 for this?
WoW likes physical cores, and on it's defaults won't use Hyperthreading. So, in your proposed scenario, I would go with the AMD 1090T. Presuming you won't use an Intel Hex core proccy, anyways, which you wouldn't be able to get for the amount of money you appear to be looking at.