Which vacuum??!! Choices are Wertheim 3030T, Kirby, Dyson dc15, Kenmore Progressive 35922???

Please help!! I need a new vacuum and I have decided this time to purchase one that actually does the job it's supposed too! Well, the price! Who would have thought such a mundane thing cost quite this much?! Do I want the Consumer Mags pick (Kenmore)?? or the trendy Dyson which everyone buys but doesn't score nearly so high in ratings but is so funky looking (for a hoover!)!!, the overly priced Kirby (off Trade Me) or the Wertheim from Godfreys which the sales people tell me is as good as the best at less?? Confusing!! I will need to take up and down stairs and the washing element is not so important to me. Upright or pull along?? Bagless or bags?? HEFA filter or not bother?? I would love to focus on more exciting issues so please help me make my decision, palm off the vacuuming on to the children and move on!! Thanks!!