Workstation at home !

Im thinking of purchasing a workstation from Dell using athome and don't want to spent much money for the processor. Whichone I should pick for SW2007 and 2009. I'm doing smallassembly(less than 50 parts) and part surfacing
should I stay with XP or go with vista?
Thx



Inteltm Core®2 Extreme QX6850 (3.00GHz/1333MHz/2X4MB L2/375W)[add \\\$1,329]

Inteltm Core®2 Quad Q9550 (2.83GHz/1333MHz/12MB L2/375W) [add\\\$619]

Inteltm Core®2 Quad Q6700 (2.66GHz/1066MHz/2X4MB L2/375W)[add \\\$659]

Inteltm Core®2 Quad Q9450 (2.66GHz/1333MHz/12MB L2/375W) [add\\\$529]

Inteltm Core®2 Quad Q9300 (2.50GHz/1333MHz/6MB L2/375W) [add\\\$419]

Inteltm Core®2 Quad Q6600 (2.40GHz/1066MHz/2X4MB L2/375W)[add \\\$339]

Inteltm Core®2 Duo E7300 (2.66GHz/1066MHz/3MB L2/375W)[Included in Price]

Inteltm Core®2 Duo E8600 (3.33GHz/1333MHz/6MB L2/375W) [add\\\$439]

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