Approximate Purchase Date: next week around Oct 5th
Budget Range: 700-800 with no rebate
System Usage from Most to Least Important: research
Parts Not Required: Keyboard, Mouse, Monitor, Speakers, OS(Planning to use Win7
Preferred Website(s) for Parts: newegg.com, amazon.com
Country of Origin: USA
Parts Preferences: Intel i5,i7 processors
SLI or Crossfire: No
Additional Comments: The computer will be used for Numerical
computings. And I don't need fancy graphic cards such as Quadro and so
on. The spec I am planning to buy is as bellow. I will be more than
happy if I can have any comments regard with my set up.
Also, I have other questions. Do we need to buy the thermal paste
separately? Do we need to buy the cables separately?
The cooler master hsf comes with thermal paste so you should be ok with it.
If your applications are heavily threaded you might get a benefit from having i7 2600k instead, and with no graphics card it would even fit your budget
Unless you intend to do gaming with the PC you most likely don't need a GPU at all.
The onboard graphics from the i5 or i7 will be quite sufficient to run things such as 1080p video if needed.
So basically what you should change is the memory to: Corsair/Gskill/Kingston/Mushkin 2x4GB 1.5V CAS9 1600Mhz ~$50-60 so not a big investment.
The PSU is solid, but check for sales on units from Antec and PC power & cooling as well, might get a nicer price.
500-650W will for sure be enough. Most likely you could even do with less especially if you don't get a video card.
Overall though you have a pretty solid build there.
I don't really know much about gpu acceleration in scientific computing but do you know if the programs you use are gpu accelerated? I know nvidia makes the tesla series for this stuff but any gpu should be able to help and gpus can greatly increase computational power with more efficiency than a cpu. If not then do as rvilkman said, drop the gpu and upgrade to the i7. In either case you don't need 650w.
Everything you need to build the pc will come with the parts, except for a screwdriver.