I have used several counter-top mixers over the past few years exclusively for dough mixing so can offer some advice...
You will find that if you make a standard 2lb loaf in either a Kenwood Chef or the KitchenAid Artisan, you will wear through the gearboxes pretty quickly. The majority of the components in them are plastic and they don't last when asked to do the heavy stuff every day. They are intended for the whisking, whipping and *occasional* dough mixing.
After wearing out the second Kenwood Chef gearbox (the grease started leaking out the front too), I tried an Assistent dough mixer from the Continent but I found it tried to walk across the counter top. That was when I started looking at KitchenAid... but the commercial ones. They are intended for a tough, always in use commercial duty cycle and all internal parts (apart from the one nylon safety gear) are metal.
My first model was the commercial Kitchenaid 5KPM5 in white which had a one-year commercial warranty. It is fully serviceable and after three years I decided to treat it to a new gasket and grease. There are folks on the web selling the appropriate parts. It was about two hours work the first time since I had to follow a guide. I saw the nylon worm gear was showing signs of light wear so after another two years I ordered more grease and a new gear. This time it was only one hour to deal with since I knew what to expect.
I still have my 5KPM5 as a "spare" mixer but have since upgraded to one of the new KitchenAid Heavy Duty mixers with the digital motor and sealed gearbox (not easily serviceable). It was much quieter than the 5KPM5 and had a larger bowl.
I should add that I had a warranty issue with the motor (a piece of swarf or something was in it and it squeaked when starting and stopping) but KitchenAid were wonderful and simply swapped it out for a new one of the same model even though I was 11 months and 2 weeks through the warranty.
John Lewis sometimes stock the KitchenAid Heavy Duty models so I would say go for it. Their warranty is excellent.