Choosing parts with an ample budget depends on what the user will use the computer for (and if overclocking is a thing). If it's nothing more than gaming, then Skylake and an AMD R9 390X or a nVidia GTX 980 Ti or two (of either) would be plenty enough for gaming at 4K resolution (currently the benchmark of high end gaming PCs and a good indicator to the next few years). If the user will actually be doing some work on the system (e.g. video editing, 3D modelling, animation, rendering, etc), then a X99 workstation build would be better (and the only case where I would say never go for AMD graphics). Also for workstations, the more graphics cards you throw in (up to 4 way SLI), the faster projects get completed.
Note about RAM, 4GB DDR3 1600Mhz is the general minimum anybody should ever get. 8GB is the average and 16GB is more than most people use (the exception being the above workstation users). On the other hand, if you choose to get more RAM (e.g. 32GB or more), you can turn the unnecessary RAM into a RAMdisk which will act like a mini SSD - good for storing cache files and other temporary files like that to speed up certain apps. Other than that, I've not heard of many other practical applications for huge amounts of RAM. Also, since X99 and Skylake both use DDR4 RAM, I've seen 2400Mhz to 2600Mhz often recommended for them.
For CPU coolers, I like Closed Loop Circuit liquid coolers like the Corsair
H100i or
H110i. Many modern cases support one or more CLCs mounted either at the rear, top or front of the case. They can be tricky to mount (depending on the case) but that way you don't have a big chunky HSF on top of the CPU blocking view to the pretty heatsinks of the motherboard.
With power supplies, if you're just using one graphics card you only need 450-500W from a reputable brand. 600-700W is if you're using two graphics cards, 750-850W if you're using 3, and 1kW+ if you're using four. Power efficiency forms a bell shaped curve, so using less than 50% or over 90% of the power capacity will result in wasted energy (and money in the long term). Also modern PSUs are graded based on their 80+ efficiency rating (bronze, silver, gold, platinum). In a PC review magazine I read this morning, the
Corsair RM750i scored 99% because of its high efficiency, modular design, and bonus features, although there were a few others in the test that scored 95% and above.
Cases... Fractal Design are famous for their quiet cases. Airflow isn't the best, but still good enough to support a pair of GTX 970s in SLI. There is no tangible benefit from good mid-tower cases and full/high-tower cases - you get more space for drives, support for eATX specs, more fans and usually compartmentalised design to create separate thermal zones for the drives, PSU, and motherboard areas. Personally, I went with a
Corsair Graphite 760T last year because of its superior cooling options, its storage design options, and its aesthetic looks. However so many cases flood the market every year that there are bound to be better options if you care to look.
Motherboards... FAST really knows his stuff when it comes to motherboards. I've been keeping track of both the X99 and Z170 motherboards as they come out, and find it difficult to choose any one to promote because of how it feels like the main players are just trying to juggle the chipset resources with the features they're trying to push forward. My favourite X99 motherboard for instance is the
Asus X99-Deluxe, but Asus also offer the RoG
Rampage V Extreme for gamers and
X99-WS for workstations. And for Skylake, I like the
Asus Z170-Deluxe but the
Asus Z170 Maximus Hero has been rated one of the best overclockers so far in tests (and best for gaming) whilst the
MSI Z170A Gaming M5 is more affordable and performs similarly in games. Soon more budget orientated Skylake motherboards will come out too.
And on storage, one SSD is pretty much as good as another (but I like Samsungs), and HDDs have become a two legged race between Seagate and Western Digital. These days it doesn't matter what HDD you get, you just get a big one for storage, then use the SSD for the OS and any games you want to load fast. 250GB SSD + 2TB HDD feels like the minimum for me, but I prefer 500GB SSDs and 3+TB HDDs because I fill both fast. In other news though, Intel-Micron have announced 3D XPoint memory which are apparently 1000 times faster, more reliable, and accurate (doesn't need TRIM) than the NAND and DRAM used in SSDs, and will be available to consumers as early as 2016. So expect next year to change up the whole market (similar to how M.2 is trying to change the SSD market).
Not much else for me to say based on the amount of information available about the user.
Rotflmao 
