HP Streams are horrible!  The processor sucks, the system hard drive is a 32GB soldered in flash chip.  As soon as you install something like Photoshop or Office and do updates you are out of space.  Do NOT buy one.  The $400 range is really hard to recommend for an avid Photoshop user, if you can save up a hundred or two more and go for an i5/i7 quad core with 16GB RAM and an SSD you'd be golden.
There are some good laptops in the $550 range for Photoshop use, such as the 
Link Removed which has pretty great specs for the price.
Of course you can also go certified refurbished, I just looked on Amazon and found an 
i5, 16GB RAM with 256GB SSD for $312 which is not bad at all.