It does look like you are overdue for a upgrade, a lot has changed, most people now only have a 2 kite quiver to get the full wind range. Other people are using a single kite to cover a range from 14-30kts with ease.
There are a lot of different kite designs around now, from bow, SLE, c, delta, bridled c and many other hybrids. A lot of these kites can be used as all round kites but excel in certain areas.
So depending on riding style, board and weight plus your skill level will all be factors when choosing a kite.
If you plan to only upgrade one kite this year than another next year a 12/13m would be a good option, it would replace both your bigger kites, then next year you could get a 8/9m to complete your quiver and get rid of all your old kites.
If you plan on only getting one kite and not looking to replace any others for a couple of years i would get depending on your weight around a 10m it would out perform both your 9 and 13m kites easily getting you going in 15kts and heaps of depower for 30+. Then keep the 16m for the light stuff or get a light wind board and just use one kite.
There are lots of options so do your homework, there will be a lot of new products released in the next 2 months so there will be a lot of reviews. Try talking to your local kite shop and grab some demo gear to try out. Or if you are looking for second hand gear there will be a lot of last years gear available allso at great prices and its all fairly easy to find reviews on.