You said you needed the pc to run for 4 years. I would save up more money to get a machine that meets your goals. The machine that Ualaa mentioned may cost you $1200+. Try pricing the items you need at www.newegg.com to find out the total cost to you. Only you know what you need. We can only make some generalizations. Ualaa made you a decent build, go to newegg and start pricing items.

Don't forget the OS. It needs to be a 64 bit OS to use more than 3.5gb of ram.

Drommon