It appears that Dell are clearing off old stock of Alienware Steam machines via Amazon.co.uk at a good price.
The cheapest option is the i3 model with GTX 860m graphics, 4GB RAM and 500GB HDD for £250
This model has the Steam OS installed but as the review on Amazon states you pick up a legit Windows 10 OEM product key on ebay.co.uk for less than £20
This effectively turns the machine into an Alienware Alpha and all the drivers are available for download from the Dell website.
Should make for a very decent Kodi machine for reasonable money,