The more features you get the more that can go wrong, and the cost does not clean any better. Do not worry about amperage. It just tells you how much electricity your vacuum will use. The most amperage a vacuum in the U.S. can have is 12 Amps. It does not mean the vacuum uses 21 amps.
Air flow is what picks up the dirt from the floor.
On an Upright, the major complaint is they do not reach under furniture. Please look at how an upright vacuum works, not just how it cleans. Many of the upright vacuums have a system in which the dirt is taken from the floor and blown up into the bag. Price is not what you look for in finding a quality Vacuum. We have enough that hits the fan in life, lets not have the vacuum do it too.