If you aren't overclocking, get something like the CoolerMaster Hyper 212 Evo for a CPU cooler. Best cooling in terms of price/performance. Most tests/reviews have shown that the only time AIO watercoolers significantly out-peform the 212 Evo is under extreme situations (aka heavy OC + torture tests). Under all other scenarios, the temps/noise levels are comparable, except that the Evo costs 1/3 to 1/4 as much. It also doesn't present the risk of a leak or of having the pump fail.
In terms of PSUs, it can get confusing. I personally went with a Tier 1 PSU, in terms of quality.
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html
An EVGA SuperNova GS (made by Seasonic) is usually pretty cheap, and is one of the top-rated PSUs.
A semi-modular PSU is just as good as a fully-modular one, as the only difference is that the CPU/MB power connectors aren't modular, but you have to use these anyway. So in my opinion, a fully modular PSU doesn't really warrant the extra price/consideration.
In terms of how big of a PSU you need, your GPUs' vendor will have a recommended minimum listed. You can also use this page to get an idea of what you'll need (its not a definitive answer, but is a pretty good estimate).
http://outervision.com/power-supply-calculator
Most people tend to WAY over-buy their PSUs (aka they buy a much beefier PSU than they'll ever need).
Keep in mind some games are still iffy on Windows 10, you may want to buy Windows 8 then take advantage of the free upgrade to Windows 10 once some of the bugs are ironed out.
I'd highly recommend you don't cheap out on the motherboard or case. Once you've worked with a quality MB/case, you'll regret having ever cheaped out on those components in the past, trust me.
Problems? See this thread at archive.org.
