I can relate, as I work in design and work with Photoshop as well. Here's my recommendation:
PCPartPicker part list / Price breakdown by merchant
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Core i7-5820K 3.3GHz 6-Core Processor | $299.99 @ Micro Center |
| CPU Cooler | Noctua NH-D15 82.5 CFM CPU Cooler | $89.89 @ NCIX US |
| Motherboard | Asus X99-DELUXE ATX LGA2011-3 Motherboard | $372.99 @ SuperBiiz |
| Memory | A-Data XPG Z1 16GB (4 x 4GB) DDR4-2400 Memory | $179.99 @ Newegg |
| Storage | Samsung 850 EVO-Series 250GB 2.5" Solid State Drive | $105.99 @ Amazon |
| Storage | Samsung 850 EVO-Series 250GB 2.5" Solid State Drive | $105.99 @ Amazon |
| Storage | Western Digital Red 4TB 3.5" 5900RPM Internal Hard Drive | $159.97 @ NCIX US |
| Video Card | AMD FirePro W5100 4GB Video Card | $322.99 @ SuperBiiz |
| Case | Fractal Design Define R4 (Black Pearl) ATX Mid Tower Case | $79.99 @ NCIX US |
| Power Supply | SeaSonic 620W 80+ Bronze Certified Fully-Modular ATX Power Supply | $85.99 @ SuperBiiz |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total | $1803.78 | |
| Generated by PCPartPicker 2015-04-04 02:08 EDT-0400 |
Rationale:
CPU: Photoshop loves strong per core performance, but I decided not to blow the budget and went with the entry 2011-3, which is a strong contender as my favorite CPU for graphic designing at the moment.
CPU Cooler: Since this is a work machine, a work machine, in my opinion, needs to be near silent. The bequiet! does an awesome job at thermals and silence.
RAM: Like PS loves per core performance, it also loves RAM. The newest versions of PS allow you to allocate as much RAM as you wish, though, at some point, the return in performance doesn't really validate the price.
Motherboard: My only thing a motherboard needed to check off is that it supports RAID, as having a large and fast scratch disc will speed up workflow immensely. The X99 Deluxe does, and does it while being a very stable board.
Storage [SSDs]: These are some of the best SSDs on the market right now, and they have fantastic read/write speeds, which can be improved by the use of RAID.
Storage [HDD]: You said your files are going to be 350-500mb. This drive could hold approx. 3500 of those files. However, I'd recommend down the road that you invest in an off shore NAS for backup purposes.
GPU: All a card needed to get my thumbs up was 10 bit color support, and support for GPU acceleration in Photoshop. The W5100 meets my demands.
PSU: SeaSonic is amazing at making good quality power supplies. This will power the K2000 and CPU with no issues whatsoever.
Case: The Define is quiet and very sleek, and would fit into a workplace very well.