Very strange graphical issues

[opspotty]

Greetings Facepunch, I am new to the forums but I have been experiencing these painful graphic glitches ever since I upgraded my computer and I could really do with some help.

The game looks like this, and depending on where I am in the map and where I look, the glitches change. Sometimes there will be red/orange/yellow/green squares, full bright with no shadows, complete whiteness and many more annoyances.
[IMG]http://cloud-4.steampowered.com/ugc/43101071523645964/6650FF34A8C5A1C2868D35390C35D960BAE60BF2/1024x640.resizedimage[/IMG]
[IMG]http://cloud-4.steampowered.com/ugc/43101071523643207/06B4D74DD8760E6A89D64E44B46BC8BD2A703EB8/1024x640.resizedimage[/IMG]
[IMG]http://cloud-4.steampowered.com/ugc/43101071523632440/198F4A5C1A5930A2F8357178B8F7B28D9CF2B4F7/1024x640.resizedimage[/IMG]
[IMG]http://cloud-2.steampowered.com/ugc/43101071523630001/12B9567E3D920C312E625CADEEB92611211B3F12/1024x640.resizedimage[/IMG]
[IMG]http://cloud-4.steampowered.com/ugc/43101071523624048/2C455DF8508EF82FF4A9B94662CC82111B096C50/1024x640.resizedimage[/IMG]

Here are my specs from DxDiag:
BIOS: BIOS Date: 11/22/13 09:33:06 Ver: 04.06.05
Processor: AMD FX(tm)-8350 Eight-Core Processor (8 CPUs), ~4.0GHz
Memory: 16384MB RAM
Available OS Memory: 16284MB RAM
Card name: AMD Radeon R9 200 Series
Manufacturer: Advanced Micro Devices, Inc.
Chip type: ATI display adapter (0x6798)
DAC type: Internal DAC(400MHz)
Device Key: Enum\PCI\VEN_1002&DEV_6798&SUBSYS_3001174B&REV_00
Display Memory: 2740 MB
Dedicated Memory: 3046 MB
Shared Memory: 3790 MB
Current Mode: 1440 x 900 (32 bit) (60Hz)
Monitor Model: HP w1907
Monitor Id: HWP26A3
Native Mode: 1440 x 900(p) (59.887Hz)
Output Type: DVI
Driver Name: aticfx64.dll,aticfx64.dll,aticfx64.dll,aticfx32,aticfx32,aticfx32,atiumd64.dll,atidxx64.dll,atidxx64.dll,atiumdag,atidxx32,atidxx32,atiumdva,atiumd6a.cap,atitmm64.dll
Driver File Version: 8.17.0010.1299 (English)
Driver Version: 14.200.0.0

I have tried many ways of fixing the issue, including:
Adding the launch parameter -dxlevel with a value of 80, 85, 90, 95, 98, 100, and even 110
Disabling all addons
Disabling all other game files
Reinstalling the game
Verifying the integrity of the game cache
Updating graphics drivers
and joining the dev beta program.
None of these have worked on this computer.

I have searched through many videos and other fdorum threads but their solutions have not worked.

Previously I had a AMD Phenom II Black Edition, 32bit Windows, 4GB of RAM, and a Radeon Sapphire HD 6770, and everyhing worked really well for Garry's Mod.

Any help would be greatly appreciated.

Thanks!