For word processing I would recommend Athlon II 270 over A4, it's more reliable and u don't even need the integrated graphic of the A4-4000, plus A4-4000 is slower and short of L2 cache. I have built one of the similar build to my friend and he was very happy w/ this fast, office helpful build.
PCPartPicker part list:
http://pcpartpicker.com/p/1qqcA
Price breakdown by merchant: http://pcpartpicker.com/p/1qqcA/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1qqcA/benchmarks/
CPU: AMD Athlon II X2 270 3.4GHz Dual-Core Processor ($53.98 @ Amazon)
Motherboard: MSI 760GM-P23 (FX) Micro ATX AM3+ Motherboard ($47.97 @ Outlet PC)
Memory: Kingston 4GB (1 x 4GB) DDR3-1333 Memory ($29.99 @ Newegg)
Storage: Toshiba 320GB 2.5" 5400RPM Internal Hard Drive ($43.99 @ Amazon)
Case: Antec VSK-3000 MicroATX Mid Tower Case ($19.99 @ Newegg)
Power Supply: Corsair CX 430W 80 PLUS Bronze Certified ATX12V Power Supply ($39.99 @ Microcenter)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($14.99 @ Newegg)
Operating System: Microsoft Windows 8 (OEM) (64-bit) ($88.90 @ Amazon)
Total: $339.80
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-10 13:22 EDT-0400)