Assuming you just need the processor and motherboard:
What parts do you want to reuse?
What are you going to be doing with this multi-monitor setup?
What are you going to be doing with the computer?
Budget?
Assuming above but also assuming office work and multi-tasking and a moderate budget:
-AMD Athlon IIx3 is excellent budget at about $75 for 3 cores at 2.9GHz.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103724
DDR3 motherboard
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131398
DDR2 motherboard (this is the board I have)(if you have ddr2 ram you want to reuse)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131595
-The least expensive intel I would recommend is the core i3 at around $120.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115222
DDR3 motherboard
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131638
-As you can see I have a bias for Asus motherboards and ATI chipsets.
-You could go even cheaper or more expensive, all being able to still do what you want. Just a matter of speed an how much you want to do at once.
Assuming you are starting a new build:
You are not providing us with enough information. I could give you about 20 configuration off the top of my head that would fit your needs between $500 and $5,000. Please try reading this:
http://www.tomshardware.com/forum/261222-31-build-advice
I especially need to know what you do and do not need. Do you need monitors also? How much are you looking to spend etc?
I'll try to respect that you want an intel processor but if the cost of the processor is less than $200, AMD really is the better deal, with the exception of the core i3 2.93GHz (dual core with hyperthreading) which is competing in the price bracket of the Athlon IIx4 2.9GHz and the phenom IIx3 2.8GHz. AMD's TLB bug is a thing of the past. How long have you been out of the game? Like what year were you last in the game?
I would post some general information also until you post more information about what you need, but everything I would say and more is summed up here:
http://www.tomshardware.com/forum/269162-31-recommended-builds-usage
The core i3 system is listed as the budget intel system.
Anyway, hope something there helped. Let me know more details and I will try to help more.