No problem. I know it can be scary, but you want to look at the amps on the PSU. Since people think a PSU's efficiency means it can output less, a lot of "experts" have spread lies all over the internet. If a website claims X system draws 400W from the wall, this means that the power draw is actually less, because the efficiency comes into play because it's converting AC to DC. This means that a system that draws 400W from the wall is in reality only 320W. The remaining 80W is turned into heat. Your 750W can supply all 750W, and if it has a efficiency of 80+, it pulls: 750 / 0.8 = 937,5 from the wall. Unfortunately this is a mistake a lot of people make, while it's not bad to buy a PSU with lots of headroom for future upgrades and or overclocking. You can save money by not doing so.