Do not confuse what workstation video cards can do vs. gaming video cards. Gaming video cards (e.g. NVidia's GT/GTX/GTX Titan) coding, GPU's, and memory are geared more towards motion/FPS (Frames per Second). Workstation class video cards (e.g. nVida's Quadro) are geared towards engineering/photo & video editing/rendering (i.e. the very applications listed).
As far as the differences between the K600 & the K2000:
1) K600:
a) Memory - 1GB DDR3
b) Memory Interface - 128 bit
c) Memory Bandwidth - 29GBps
d) CUDA Parallel Cores - 192
e) Simultaneous Displays - 2
f) Monitor Connections - 1 DVI-I (Single Link 18pin) & 1 Display Port (DP)
2) K2000 & K200D:
a) Memory - 2GB GDDR5
b) Memory Interface - 128 bit
c) Memory Bandwidth - 64GBps
d) CUDA Parallel Cores - 384
e) Simultaneous Displays - 4
f) Monitor Connections:
I) K2000 - 1 DVI-I & 2 DP
ii) K2000D - 1 DVI-I, 1 DVI-D (Dual Link 24 pin), & 1 mDP (mini)
Long story short, for what you are listing for expected work/software load, go for the K2000 line if you can afford it. The GDDR5 memory is markedly faster that DDR3, and it has 2x the amount. Any serious Autodesk/CAD work and/or Adobe CS6 will quickly drag the K600 down. Also, neither the K600 or K2000's require a separate connection from the PSU. As their Watt draw is <75W, the PCIe slot (PCIe x16) can power the cards.
Now as to which K2000 to go with, for what you listed, especially the CS6, you definitely want the K2000D. With the DVI-D port, you can drive the proper bandwidth and color to an IPS display (all of which are DVI-D. You can then use the DVI-I port to power a quality TN display for the regular text/low graphics draw work.