Will this be a custom computer built by either yourself or the local shop?
If so, there's tons of information in the hardware section.
As Easyscor said, wait if you can. No requirements for AH3 haven't been carved in stone yet.
If you want an intermediate AH3 capable computer, there's some basic advice applicable to most anything.
A quick and rough compilation using
www.partpicker.com:
PCPartPicker part list:
http://pcpartpicker.com/p/yFKfTWPrice breakdown by merchant:
http://pcpartpicker.com/p/yFKfTW/by_merchant/CPU: Intel Pentium G3258 3.2GHz Dual-Core Processor ($64.88 @ OutletPC) upgradeable to i5-4690K (+165) or i7-4790K (+263)
Motherboard: MSI Z97 PC MATE ATX LGA1150 Motherboard ($82.88 @ OutletPC)
Memory: Mushkin Silverline 8GB (2 x 4GB) DDR3-1600 Memory ($34.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($46.89 @ OutletPC)
Video Card: Asus GeForce GTX 970 4GB STRIX Video Card ($296.99 @ NCIX US)
Case: Cooler Master Elite 430 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: SeaSonic 650W 80+ Gold Certified Semi-Modular ATX Power Supply ($90.98 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.45 @ OutletPC)
Operating System: Microsoft Windows 7 Home Premium SP1 OEM (64-bit) ($86.75 @ OutletPC)
Total: $750.80
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-09-29 07:03 EDT-0400