An early action should be to talk to your electricity distribution company (assuming that you wish to connect to the grid). Depending upon your local distribution layout, you may well be limited to 6KW output. In Cumbria, United Utilities state that they will respond to queries within 90 working days and my experience is that they aim to take as near as 90 days as they can. At the 5/6KW level, Proven and Iskra are the two most often seen. I have a Proven 6KW, I had some teething problems, which seemed to take a long time to get sorted, However in the grand scheme of things it was not that long and it has worked without fault once the problem was identified and fixed. Choice may depend upon who has the nearest installer or which one you like the look of best. With the Proven, I would recommend going for the 15m tower, it does not cost that much more than the 9m tower yet puts the turbine into cleaner, faster wind.
You can see my output figures on the spreadsheet. The figures show my wind to be 4.2m/s at 10m. However local topographical features, such as the shape of exposed trees suggest that the wind is at least 6m/s according to my installer, Miles Postlewhaite of Turbine Services who has considerable experience in the industry.