Kitchenaid resorted to using a plastic transmission cover a couple years ago that caused a firestorm of complaints and returns as it was prone to cracking. Since then they have been using a far stronger aluminum one. I have a brand spanking new KA pro 500 that works very well. My old (3 years) Pro 600 cracked it's transmission cover and did some gear damage. Not worth fixing. KA (Whirlpool) has great customer service. Because the KA is always evolving, I would recommend it. If you have room, I would suggest a bowl lift model over a tilting head.
A brand I would definitely stay away from is Viking Professional. It is a Chinese made machine (Made in PRC - Peoples Republic of China). They are generally only available in boutique culinary shops. A lot of these places have very limited return policies. Some will refuse to take back products that have been used even only once. If you need warranty work done, Viking forwards the call to a repair shop in Detroit, Michigan. You will pay an arm and a leg for the machine compared to a KA (usually about $700 Cdn) and their customer service is dreadful. Yes, I am speaking from experience. They don't fare well in tests and reviews either and I know first hand that although they appear rugged, they are overrated.
I know people with Bosch and De Longhi and they love their machines and all the available attachments. I would stick with KA, Bosch or De Longhi for something relatively affordable (300-500 bucks depending where you shop). If price is no object and you want a real multi use machine, say for mixing concrete, a Hobart is incomparable.
In my experience with any of the affordable machines that I mentioned, it is important to be true to the recipe and follow the manufacturers guidelines with regard to dough hook speed. Making dough is a real test of a machines abilities, especially pizza and bagel doughs. Until you get used to the machine, I wouldn't go to far from it while it's operating. It's fairly easy to overload these machines and you will need to be there to shut it off quickly if you do. If not, you can do some serious damage.
Happy bargain hunting.
