You probably better off buying one and upgrading the RAM yourself. RAM is helpful if your doing something like rendering full 1080p HD videos or doing some photoshop work with large very high resolution photos. In short, more RAM is used by professionals a lot because they are working with much bigger files and their applications, such as photoshop tend to be larger. If your an average user, web browsing, email, maybe a little iMovie, then the stock 4GB of RAM should do just fine for you. That being said if you end up needing more RAM down the line, you can add RAM pretty cheaply. If you want more speed, and by speed I mean faster start ups, applications and files loading faster, then you want an SSD. An SSD is super fast because its basically one giant thumb drive and unlike a HDD it has no moving parts so nothing has to rev up to read or write data. SSDs are still a touch pricey but the price is coming down. I just picked up an Intel 520 240GB for $350 total, so that wasn't too bad. But I hoped this helped a bit.
