That Pugetsystems article is contradictory. First they say cores/threads are not beneficial because most Photoshop processes are single or lightly threaded, and that Photoshop is not optimized well for threaded processing or utilizing additional cores, then they turn around and say it IS, up to 8 cores, and all of the CPUs they recommend are models with at least 4 cores and 4 hyperthreads. While I generally applaud most of their testing and articles, whoever wrote that one must have been smoking dope. A thing either IS or IS NOT, beneficial. If it's beneficial SOME of the time, then it's beneficial PERIOD.
Multi-threaded actions hit a point of diminishing returns after around 6 CPU cores, and most completely stop improving after 8 CPU cores. This includes effects like color mode conversion, many blurs, hue/saturation, brightness/contrast, and shadow/highlight. The best multi-threaded effect (converting to Lab Color mode) had a decent multi-threading efficiency of about 94%, but most of these effects had an efficiency closer to 80% which isn't so great.
One thing we want to point out is that the raw number of cores different Photoshop effects can utilize is only a starting point when choosing a CPU for Photoshop. Even though Photoshop may at times be able to use eight or even ten physical CPU cores, our testing has shown that it doesn't typically do so very effectively. Because higher core CPUs also tend to have lower operating frequencies, this means that the best CPU for Photoshop will be one with a moderate core count but a high operating frequency.
After examining the results of our testing, we believe that - of the Intel CPUs available at the time of this article - the following three models should give you the best possible performance in Photoshop CC:
Recommended CPUs for Photoshop CC
Intel Core i7 4790K 4.0GHz Quad Core 8MB 88W or
Intel Core i7 6700K 4.0GHz Quad Core 8MB 95W
Intel Core i7 5930K 3.5GHz Six Core 15MB 140W or
Intel Xeon E5-1650 V3 3.5GHz Six Core 15MB 140W
I've found it to be beneficial in my own usage, AND since they were likely using a test bench rig and not running any other processes or applications during their testing, which most people WILL be doing, I'd say their results in this case are probably not as relevant and conclusive as most their testing usually is.
Also, Adobe's own dev team has indicated that MANY processes, but not all, in Photoshop, DO advantageously use hyper or multi-threading when it's faster. So some functions of Photoshop do use it while others do not.
CorelDraw definitely uses threaded processing to it's advantage as well. Saving and running various effects and processes are much faster on a quad core or higher chip than they are on say, a G3258. All that being said, it IS doubtful more than four cores/threads will ever be utilized in either of those programs which is why I suggested the much less expensive i5 might be a good choice and would allow for a more powerful GPU card, which is likely to have some affect on graphics performance as well, depending on the type of image processing you're doing.
If you will have tabbed web browsing, multiple simultaneous applications or other utilities running at the same time image processing is going on in either of those applications, it's likely you'll benefit from a 4/4 chip, especially considering windows is going to be running some processes of it's own in most cases and on most systems.
Personally, since it uses both the strengths of a fast core AND somewhat uses threaded processes, I'd say any four core or higher chip, unlocked, and overclocked, is a very good option. A 4690k or 4790k, clocked at about 4.5Ghz on a halfway decent board like the Gigabyte Z97X-Gaming 5 or ASUS Z97-A, would probably benefit from the faster core clock in all areas where threading does not offer an advantage.