How many recessed lights should I install in my living room?
The questions you are asking are two fold.

1: How much light do I need to provide good visibility in this room - Lumens / Coverage.

2: Aesthetically what will this look like - good or awful ? Beauty is in the eye of the beholder. 

What is the layout of the six lights ? You did not mention - 3 and 3  along the long length or otherwise.

See the example below I think it will help you to decide. get a lamp of at least 800 lumens - you can get 75 watt equivalent for your recess assemblies which would be about 1000 lumens and that would make the area really bright. LEDs are pretty cheap and I would suggest you use them as well.