to the op..there are vendors like seasonic that make there own power supplys. then there are vendors like the one you posted that dont make there power supply..they just relabel brand x or y power supply. the good vendors test brand x power supply or y power supply so that it meets a set level of quality assurance. (qa). if the vendor does that then most times brand x or y power supply will be fine and last years. the problem is some power supply vendor cheat on the output that there power supply's can output or the parts they use. when that happens you get a lot of ps that are doa or blow up and take out your gaming rig. google helps people pick the right one if they use google and look at web sites like tom and hardcops that load test and open power supplys and see how made what power supply and how well it was made.
Okay, since i don't know exactly what your intent is I'm guessing gaming and some overclocking. That said you've made some very good choices. My thoughts:
1. If you have access to a Microcenter you can get your Motherboard and CPU for $275 before taxes. Its a combo deal and you have to go to the store to pick up.
2. PSU: I'd select PC Power and Cooling Mk III 600 watt. Thrifty and silent !
3. RAM - as long as it's 1.5 volt should work fine. If you go to the ASRock website you can see approved RAM for each of their Mobo's.
4. Youtube 'newegg computer build' parts 2&3 watch, listen & learn. I just built my first and that's about all there is to know.
5. I'd suggest a SSD (120 GB min) at this price range. It's another $100, but you will never regret it. I got a Intel 330 180 GB and it is awesome.
Not the best - reused the 6850, however power on to ready (with password entry) is just under 30 sec every time. Quiet and Fast.
The above website also shows best price for the components you select. May save you a buck or two. Prices change daily. If you have some time - shop, buy with rebates and you can save hundreds ... if you have the time and are cheap - like me