Unless you absolutely LOVE one of these pieces, do not purchase a one.

I'm assuming you mean that you don't know how many sofas etc. you should buy from the example you've enclosed.
If you have the dimensions of the space, with windows and doors, you could use one of the free online roomplanners (for instance: http://www.urbanbarn.com/Room-Planner) and play around with furniture arrangements. Be wary of the dimensions of the furniture, because it isn't always to the correct scale, but it is pretty easy to work with and it gives you an idea of what you could do.

Have you started an ideabook yet? You can do that here on Houzz and browse through the living room photos available and add them to your ideabook. Start one for your dining room to if you haven't already. It will give you lots of ideas. Look for window treatments, furniture arrangements, colours...

Good luck. (I hope you're considering to change the wall treatment in the dining room. I personally find that hideous.)

christelaoun, if you like more reactions, please don't start yet another thread about the same dilemma, but just do another cry for help in a comment under here. It will bring it back to the top of the list. Otherwise it all gets very confusing.

Good luck with your dilemma.

Depending on the style of furniture you choose, I would invest in a rectangular or even circular area rug to tie the seating area together. You may want to create a separate sitting area with a chaise lounge, or over sized chair with a floor lamp, a great piece of pottery or basket in front for blankets. Just a few thoughts. :)

I agree with the above advice about either hiring a decorator or taking advantage of the idea books and online programs available. I have a similar living and dining area. Even as a designer, it's been a challenge. :)

I'd love to see the finished product.