Not sure I quite understand, but I recommend something like these specs:
1) Intel G3258 CPU
2) 1150 socket motherboard (reasonable quality)
3) 4GB DDR3 memory (single stick of 1600MHz)
4) graphics card with three outputs supported at same time (will need to carefully verify which cards work)
5) Windows 10 Technical Preview ? (because it is free for several months and probably shouldn't have any major issues on a fresh install)
etc.
Can use PCPARTPICKER as a guide
http://pcpartpicker.com/p/924nNG
About my build:
If you don't need much for the GPU which you imply, you can just use the iGPU in the CPU for your needs. I had a different motherboard until I realized you'd want an HDMI output from the main board.
You should be able to run HDMI from a DVI connection with either an adapter or just buy a DVI to HDMI cable. There would be no sound but you can't run multiple sound outputs anyway so if you need HDMI audio do that from the motherboard output.
You'll need an addon card to drive another monitor (or two) and that's pretty cheap so I recommend a fanless HD6450 for that. So for about $300 this may suit your needs.
DVI-> HDMI cable: http://www.monoprice.com/Product?c_id=102&cp_id=10231&cs_id=1023104&p_id=2661&seq=1&format=2