I want to know what that someone has been smoking tbh.
The only part I'm remotely worried about is the HDD as I've never really used Hitachi's. They're supposedly very good today. I'd upgrade the CPU cooler sooner or later. It still is equal or even beats the H55. (lowest-end AIO watercooling setups, like the h55, are VERY bad)
For the HDD, I'd go for a WD Black. It's 88USD though, so you'll end up at about 742USD on using this one over the Hitachi.
As for the CPU Cooler, quite a few picks there but that's going to cost you considerably more. NH-D15 or 240/280MM AIO Watercooling setups require either a case with such mounting vents or be able to support the height of an NH-D15.
The NH-D15 runs for about 90USD, the better 240MM are at least 100USD and up.
Both the builds you posted have rather... less 'good' CPUs. A dualcore CPU for modern gaming is just no. It's good for casual gaming but if you want more performance and/or longevity, you're better off with a quadcore.
The AMD one is... well, AMD CPU. The top tier CPUs are Intel only. Mainly due to performance of when just one core is used from the 4.
Both builds only have 4GB of RAM. This is a flat out NO.
Either way, I've poked around yet again since I felt I could do better (forgot the max of 750USD ):
Snow, what sort of performance can you expect from that first $700 build you posted? for hardcore gaming would there even be any benefit if you spent an extra $300 or is that just throwing money away for performance you dont really need?
It should be able to handle most, if not all, new games without too much trouble (unless it's shit optimized etc). It should handle pretty well for at least 2 years.
I'd primarily spend the extra 300USD on a better case, ssd and cooling. Perhaps get the top tier i5 which is only about 30USD more. Depending on if you want to OC, probably a better mobo as well. Another possibility is another 8GB of RAM (16GB total) but that depends on what you plan to do. 8GB should still be good enough these days.
edit: derp. I have a 660Ti right now and it handles Skyrim with heavy ENBs on Full HD pretty well. If there's a sudden FPS drop, it doesn't go lower than 40FPS.
I'd get it myself. A good quadcore and a good high-end card is all you really need for gaming.
Z97 is the chipset used in the motherboard and correlates directly in what it can and cannot do. Z97 over Z87 brings very little new things with it so it's not much of a big deal. There's also H87 but that's more for cheap people and/or PCs needed for office-jobs.
Fans are primarily an extra. They can have a direct effect on temperate and noise levels. If you're on a 750USD-ish budget, I wouldn't get new fans. The good ones easily cost 20 to 30USD.