You could actually do it yourself. If you are in the US, NewEgg is a good place to shop. There are also plenty of options for having it custom built by others. My computer quit earlier this week and I started looking at parts to replace. As it turns out, I'm just getting a new PSU.
For a socket LGA1155 performance (overclocking to 4 GHz) motherboard and Intel i5-2500K CPU, I was looking at around $300. This is the lowest price for these components to achieve what you are asking. My find was that a good 750W modular PSU can be had for $90. Get at least a GTX560 video card (I haven't looked at cost). Get 4 GB of appropriate RAM for motherboard and CPU (small impact on performance - I haven't looked at cost). Case, HD, DVD drive can be had cheaply or more expensive depending on your taste (little impact on performance).
The above are minimum requirements upon which you can improve by spending more money, but FPS per dollar spent will not be very dramatic beyond this point.
Last edited by Art_P; 07-28-2012 at 05:58 PM.
MSI P55-CD53, Intel i7-860-3.7Ghz, NVida GeForce 560 - 1GB, 4GB SDRAM DDR3 1333, WD 750GB-7200rpm-32MB, Windows 7-64 bit
Acer 23"WS LCD and Benq 19" LCD, CH yoke and pedals, Logitech Extreme 3D Pro, TrackIR 5, FSX Deluxe w/Acceleration, UTX-USA, GEX, ASE, WOAI, ADE, FSDS