It is not impossible to reach 5ghz on the asrock but i can neither guarantee it. Each processor chip is unique in how far it can go. Some are good and some are not as good. All i am trying to say is that there is a lot of money and performance loss just by picking out the elite of components that nobody can guarantee you the numbers. People with asrock and cm 212 reach 4.4 easily, some with A70 reach 4.8ghz, some stumble at 4.2... there is no singular and fail-safe pattern here. LLC1 for power btw.
To answer your curiosity on the ripjaws as well as the cm 212, from time to time computer parts become a trend. Ripjaws is a fine piece of memory and no doubt about it. They had an unbeatable price for months straight. Combining their good performance and 1.5v it is a killer product and bang for buck. That doesn't mean it is perfect for everything. It's design on the heatspreader is uncomfortable for the big heatsinks. It became a norm along with cm 212 because you can raise the fan positioning a notch and accommodate the ripjaws. Speaking cold mathematical facts, real life performance between the ripjaws and any other credible manufacturer's memory at the same speeds is unfelt. The same cannot be said for the hyper 212 though. The company has made a goldmine of that cheap heatsink, and yes it is adequate for overclockings of 4.0ghz-4.4ghz but not much further. The components it is bundled with are lacking (no second fan, no extra bracket, no decelerators, mediocre to bad thermal paste). But it is cheap! And for that exact price no other cooler can beat it. It doesn't make it a splendid heatsink but just ok. If you start moving fans up though it compromises it's already medium performance. Once well established as a good cheap heatsink it is VERY hard to dethrone it no matter how much other companies try. My personal favorite budget heatsink is the Corsair A70 which for a few bucks more comes with all it needs to fire up your 2500k beyond the 4.5@1.35v (again the same chip rules apply).
This again doesn't make A70 the perfect heatsink, just a better solution a little more money.
PSU questions:
CX, GS, TX, HX, AX that is the branding for corsair's different tiers of PSUs. CX is the average, not so great, entry level psus. They are solid, no question about it, but the offer just the basics, often interpreting in no modularity, no more power draw than the named one and not that great efficiency (the rate of socket-to-computer watt %). The higher the tier the better the quality and the benefits. Don't just look at corsair though. I might build a computer with an OCZ or a Corsair for low needs, or thermaltake toughpower if i want more watts just for headroom. Enermax, Antec, Corsair, Lepa, Cougar, Seasonic, Superflower are all solid psu's. Practically no-brainers. For all the other companies i suggest you read a review on them first.
If the price for the extra mile from a 650watt psu to a 850watt one of equal quality is small and you know you always want to be on top of the game and got the money to spare (let's say about 20$ more) then go for it. If you know you won't be upgrading after this purchase, well then save the 20$ and put it somewhere else.
HDDs. In short, no mechanical hdd will saturate the sata2 controller. In other words the protocols are the same and there isn't even a switch between sata2 and sata3 like it used to be between sata1 and sata2. The fact that sata3 is double the size of transfer rate of sata2 means nothing if your component runs bellow 3gb/s. Only ssds can take advantage of the 6gb/s controllers atm.
I like super-extreme OC too just as long as i don't have to pay the money difference between i5 and i7 to achieve it, and the i5 won't get toast in the end