CPU - You are going with an H61 motherboard which means no overclocking. If this is by design, then change the PCU to a non-K version. Otherwise, you will need to be looking at a P67 or Z68 motherboard to take advantage of the unlocked K series CPU and overclock. Don't forget an aftermarket CPU cooler if you plan to overclock (Cooler Master Hyper 212 EVO or the older model Hyper 212+ is fine).
MEM - Just be sure those Vengeance modules do not have tall heat spreaders and are 1.5v.
GPU - The 550 Ti is probably not the best choice at its price point. Typically an HD 6850 or HD 6870 can be found for similar pricing and offer better performance.
PSU - Get a branded one! Corsair, XFX, Antec or Seasonic.... 500w is plenty of power for a single GPU setup.
HD - IMHO, the only good Western Digital is a Black drive. Seatage or Samsung if you can.
sadams said it first so won't be repeating: so here it is....
no need for 2500k unless you get better MB
these days any memory manufacturer is fine so look mainly on price 1600Mhz is fine
Graphics can't argue there 6850 or 6870 nvidia just can't compete at the price
PSU oh boy oh boy non brand...good luck with that Get antec, corsair, seasonic
HDD you can use green for storage but do your self a favour get 60 SSD for OS or 120 SSD and ditch green. You can go by with 120 SSD ...no need for HDD unless you download like a maniac.
Monitor...unless you are space restricted get at least 22-24" some are like $140 or less