A lot will probably change between now and December, but here's a few things to think about.
First, you are going to want to take advantage of dual channel ram. Get 2x4GB sticks instead of 1x8.
Also, I would suggest the AMD Athlon II x4 750k as a CPU. It's on the FM2 socket, but is really the best value in CPUs under $100 right now. It can be had for under $80 when it's on sale. It is also multiplier unlocked so it can be overclocked for substantially better performance.
I would recommend a build that looks something like this.
[PCPartPicker part list](http://pcpartpicker.com/p/1Ajpa) / [Price breakdown by merchant](http://pcpartpicker.com/p/1Ajpa/by_merchant/) / [Benchmarks](http://pcpartpicker.com/p/1Ajpa/benchmarks/)
Type|Item|Price
:----|:----|:----
**CPU** | [AMD Athlon II X4 750K 3.4GHz Quad-Core Processor](http://pcpartpicker.com/part/amd-cpu-ad750kwohjbox) | $79.99 @ Amazon
**Motherboard** | [Asus F2A85-M PRO Micro ATX FM2 Motherboard](http://pcpartpicker.com/part/asus-motherboard-f2a85mpro) | $89.98 @ Outlet PC
**Memory** | [Corsair Vengeance LP 8GB (2 x 4GB) DDR3-1866 Memory](http://pcpartpicker.com/part/corsair-memory-cml8gx3m2a1866c9b) | $57.99 @ Newegg
**Storage** | [Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive](http://pcpartpicker.com/part/western-digital-internal-hard-drive-wd10ezex) | $59.98 @ Outlet PC
**Video Card** | [MSI Radeon HD 7770 GHz Edition 1GB Video Card](http://pcpartpicker.com/part/msi-video-card-r7770pmd1gd5) | $69.99 @ Newegg
**Case** | [Corsair 300R ATX Mid Tower Case](http://pcpartpicker.com/part/corsair-case-300r) | $49.99 @ Newegg
**Power Supply** | [Corsair CX 500W 80 PLUS Bronze Certified ATX12V Power Supply](http://pcpartpicker.com/part/corsair-power-supply-cx500m) | $34.99 @ Newegg
**Operating System** | [Microsoft Windows 8 (OEM) (64-bit)](http://pcpartpicker.com/part/microsoft-os-wn700404) | $88.88 @ Outlet PC
| | **Total**
| Prices include shipping, taxes, and discounts when available. | $531.79
| Generated by PCPartPicker 2013-09-05 15:16 EDT-0400 |
It's probably not the absolute best specs for the money, but I like to spend a little extra on a reliable PSU, nice case, and better motherboard. It just makes the build a little more well rounded.