XPS 8700 with stock 600 PSU??

I was searching on amazon just out of curiosity and found that theirs tons of different configuration for the xps 8700. I decided to click on the most expensive config that's 5000$ and i was astonished to see that it came with a stock 600 watt PSU. Why couldn't dell have included that PSU in all the other xps 8700's instead off the 460W one to allow for better future upgrades because i want to get a gtx 970 but will have to pay an extra 100$ just for a better PSU. Also, how come some of the pictures i see has the XPS 8700 with a red motherboard? the one i have is green. is their any difference between the two?

Heres the link for the best XPS 8700 configuration possible: www.amazon.com/.../ref=sr_1_1;ie=UTF8&qid=1433471066&sr=1-1&keywords=xps+8700&refinements=p_n_availability%3A1248801011%2Cp_36%3A2421884011