Are you planning to build or buy? If you want to build, you'll probably be able to get a bit more power out of the same budget, but you'll risk frying the parts without proper precaution.
Either way, I'd reccomend doing a lot of research. For example, Intel's 7th generation processors don't really have a speed advantage over 6th generation but cost a lot more (native 4k video streaming is the only difference that I really know of.). AMD has also supposedly put forward a much cheaper CPU that is actually comparable to Intels (but I haven't had a chance to check out avtual benchmarks.).
Buying is completely different and I'm not really sure what gaming rigs you can get, if any, for $750
If you do decide to build, then the LinusTechTips forums are a great place for information on parts, prices, and other just general computer things.
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