Back again!
Sallyho, can you describe what types of carpet you have? Are they loop-pile or cut?
What must be considered is that the best vac for your tiled floors will not be the best vac for your carpets and upholstery/bedding etc. Any single vac will be a compromise. As I said before, an upright (with integrated powerhead) will be much more effective on carpets, but there's no benefit of that on a hard floor.
If you are a clean freak and are happy to vac regularly, you can get by with a good suction cleaner without a powerhead. Only you can determine where your priorities lie.
A good upright would be say a Dyson DC14 (HEPA) R.R.P around $900
There are some good vacuums made by Sebo including the new Dart series.
The Kirby range is grossly overpriced and very old technology and heavy, but well made.
Filter Queen make very good hi filtration vacs.
Do you have any types you've looked at or considered?
Ash.