ZBrushCentral

Need upgrade advice

I have money to invest in upgrading my existing system.
One of the reasons for keeping the existing hardware is that I wish to keep
Windows 7. I would rather scribble on a wall of a cave than use Windows 8
In any case, have about one thousand dollars to spend (maybe more if situation warrants)
Have a phobia about looking at technical specifics but there us a program called Speccy that
gathers the information for you.
The programs in use are Zbrush, Key Shot (regular and Zbrush version)Maya 2012, Adobe Photoshop CS6
and DAZ Studio. What I am looking to do is primarily speed up KeyShot but from what I gather a different
graphics card might not be the total solution (CPU dependent).
This is my exisiting system, any advice on upgrading would be a appreciated.
Thank you.
Operating System
MS Windows 7 Ultimate 64-bit SP1
CPU
Intel Processor @ 3.50GHz
RAM
15.9 GB
Motherboard
PEGATRON CORPORATION 2AD5 28 °C
Graphics
V196L (1024x768@75Hz)
SMS27A550H (1920x1080@60Hz)
NVIDIA GeForce GT 630
Hard Drives
2930GB Western Digital WDC WD30EZRX-60MMMB0 SCSI Disk Device (SATA)
488GB Seagate ST500DM0 ST500DM002-1BD14 SCSI Disk Device (SATA) 29 °C
Wacon Intuos 5