Proper staging can really help sell a home. Yes, there are people who are very good at envisioning their own stuff in a blank space, but there are twice as many people who can't. Haven't you ever seen one of those real estate shows where a couple is looking at a new house but show a lot of resistance to one based on something as silly as them not liking the color of paint in a room? A couple of cans of paint, a paintbrush, and a couple hours of unskilled labor is all that's standing between them and a really nice house, but they can't get past that ugly color and picture a nicer one.
My parents sold their house about 4 years ago. They had appropriate sized furniture for all the rooms, fresh paint, newly redone kitchen & bathroom (my father did these himself). The house received multiple offers within a week of going on the market and they closed about a month later. The family that bought the house was a growing one & with 3 new kids since buying, outgrew it and had to sell again. However, they moved all their furniture out even before the RE photos were taken, and I'm sure the house didn't show nearly as well. It was on the market for over a year and sold for close to 20% less than asking, well under what they'd paid my parents for it 4 years ago. The market here has been up & down a little since then, but overall relatively flat. To me, the biggest difference(s) between the two sales were the online photos and complete lack of staging.
That said, leaving ugly furniture and/or clutter in your house when you're trying to sell can be worse than leaving the house barren. Really, you're trying to put "make up" on your house in a way that flatters it the most.
OP, to your original question, I agree with other posters in their advice to avoid RAC and look at Craigslist and tag sales to pick up basic, functional furniture that you can 'dress up' to show off your space.