Don't buy that crap TigerDirect is offering, the Ultra Power Supply is one of the worst products on the planet. Don't buy the Corsair Vengeance Memory I have a kit, the heatsinks are cheaply made and there just to tall (they interfere with a lot of heatsinks). Buy a set of G.Skill instead. And 6GB is out of the question, the memory controller for the i5 2500 and i7 2600 (K or non K models) is a dual channel controller which means it optimal configuration is in sets of two modules. 2GB (2x1GB), 4GB (2x2GB), 8GB (2x4GB) or you can double up with 4GB (4x1GB), 8GB (4x2GB) or 16GB(4x4GB).
On your budget I would go with these
Newegg.com - G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBXL
On your budget I would go with these
Newegg.com - G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBXL