Keep an eye out for the Godfreys sales - they are usually quite good, and there seem to be a few of them at this time of year!

Bagless are great - I recently retired my Nilfisk too and replaced it with a dyson - my DH is using the Nilfisk for reno cleaning so it still works OK, just doesn't have the suction. Bagless are DIY clean usually which is great for maintaining suction. Power heads definately help with carpet with young kids, specially if you have animals on the carpet as well.

You could go a wet/dry vac which my parents have, I loved using it cause I would shampoo the carpet about once every 6 months.