How is this for a minecraft computer?

Honestly dude, that PC would absolutely DESTROY Minecraft at 1080p. That config is good for Crysis 3 at medium to high settings at 1280x1024. And Far Cry 3 at medium to high settings at 1280x1024.

Bottom line: it will KILL Minecraft.
 
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD FX-6100 3.3GHz 6-Core Processor (£82.33 @ Scan.co.uk)
Motherboard: Gigabyte GA-78LMT-USB3 Micro ATX AM3+ Motherboard (£38.69 @ Ebuyer)
Memory: Corsair Vengeance 4GB (1 x 4GB) DDR3-1600 Memory (£28.97 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£46.85 @ Aria PC)
Video Card: Asus Radeon HD 6450 2GB Video Card (£38.99 @ Amazon UK)
Wireless Network Adapter: TP-Link TL-WN722N 802.11b/g/n USB 2.0 Wi-Fi Adapter (£8.39 @ Aria PC)
Case: Cooler Master NSE-200-KKN1 MicroATX Mid Tower Case (£33.65 @ Dabs)
Power Supply: XFX 450W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply (£34.99 @ Maplin Electronics)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer (£12.98 @ Novatech)
Operating System: Microsoft Windows 8 (OEM) (64-bit) (£69.99 @ Dabs)
Other: Monitor (£101.99)
Other: Keyboard (£18.00)
Total: £515.82
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-09-07 15:47 BST+0100)
 


This is much worse. the GPU is trash and worse than normal integrated graphics.
The CPU is trash. AMD said this themselves.

Go with the original build you had, OP
 


Do you realise the way you type is very provocative? Just thought someone should let you know.