NedxO,
Some of the choices- especially the graphics card, will depend on the priorities of use CAD applications. The best cost / performance ratio CPU is the AMD FX 8350 "Eight Core"(4.0 / 4.2 GHz)- that on Passmark is ranked No. 39 with an average CPU score of 9129 and costs about $200. For reference, an i5-4570K (3.2GHz) is No.96, score = 7128, also about $200. The prices are quite similar, but the AMD has the edge in native clock speed and general performance.
For a system also running CAD system, I would suggest using a CUDA-based card, a reasonable level GTX.
Here's a modification of a system idea I had a couple of weeks ago >
BambiBoom PixelPusher CadoGraphicamatic iPlotGame WalletScreamJoy Amdisty VI ™$#©™_7.6.13
CPU >
1. AMD FX-8350 Vishera 4.0GHz (4.2GHz Turbo) Socket AM3+ 125W Eight-Core Desktop Processor FD8350FRHKBOX > $200
2. [optional CPU cooler]
3. GIGABYTE GA-970A-UD3 AM3+ AMD 970 SATA 6Gb/s USB 3.0 ATX AMD Motherboard > $110
4. AMD Radeon™ RE1600 Entertainment Series 16GB (2 x 8GB) 240-Pin DDR3 1600 (PC3 12800) Desktop Memory AE316G1609U2K CAS=9 > $112.
5. EVGA 02G-P4-3657-KR GeForce GTX 650 Ti BOOST 2GB 192-bit GDDR5 PCI Express 3.0 SLI Support Video Card > $160.
6. Western Digital WD Black WD1002FAEX 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive > $90
7. CORSAIR CX430M 430W ATX12V v2.3 80 PLUS BRONZE Certified Modular Active PFC Power Supply > $50.
8. ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - OEM $17.
9. Antec Three Hundred Black Steel ATX Mid Tower Computer Case > $60.
10. Microsoft Windows 8 Professional 64-bit OEM $86
Monitor >
11. Acer G246HLAbd Black 24" 5ms Widescreen LED > $140.
_____________________________
TOTAL = $1025.
All of the above is from newegg except the OS from "eValue". Some items can be purchased for less, the FX 8350 is seem at $180 for example.
The performance should be very good in both gaming and CAD. On Passmark, a system with the 8350 , the Gigabyte GA0970A-UD3, GTX 650ti, 16GB RAM, Hitachi mech'l drive rated 2254 > CPU= 9991, 2D = 634, 3D= 2805, MEM= 1278, DSK= 678. The WD Black should make a disk score over 900. I would say excellent cost / performance ratio.
Cheers,
BambiBoom