One thing to note: Intel obsoletes their CPU sockets when upgrading:  ex. a socket 1156  i7 CPU will be obsolete literaly in 2 weeks with the introduction of sandy bridge. The new socket is numbered 1155 and incompatible.


AMD tends to upgrade their chips that plug and play in an existing motherboard.  


I would recommend getting a SSD boot drive - it will be as close to instant on and response you can get...  64GB's are priced at $99 at www.microcenter.com  Ues the old tech mechanical HDD as data storage. RAID 0 is 2 HDD's wired together - if one goes u lose everything...  


If looking at a +$1k price point:  a i7-950 + gigabyte 58 mobo + 8gb 1333 ram + ssd + hdd + Blu-ray/DVD writer + W7x64 + 850w psu + case + Geforce 460 or better  Geforce 580 GPU:  is gonna work for along time and can be overclocked from stock 3ghz to 4 ghz if the need for more speed is in the future...