Does GPU RAM matter, and which power supply?

Hello! I've searched the forum, but can't find much of an answer.

I'm about to purchase R9 390 4GB editions. Does the RAM matter? This https://blog.simpleblend.net/building-an-ethereum-mining-rig went with 8Gb to be "safe". Is there something else that I should be looking at regarding the DAG?

Which power supply should I go with?

https://www.amazon.com/Corsair-RM1000-CP-9020062-NA-1000-Watt/dp/B00EB7UIZU/ref=sr_1_1?ie=UTF8&qid=1469231795&sr=8-1&keywords=rm1000

or

https://www.amazon.com/gp/product/B00CGYCNG2/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER