We have this Bissell - £138 from Tesco and it does a pretty good job. It doesn't heat the water up (you put in warm water from the tap) but does have a carpet beater bar thing and a fairly good suction to get the water back out (you still have damn carpets but not sodden when its done). The bissell liquid wash isn't cheap, but does a fairly good job.
Do be aware though that it's a CLEANER not a STAIN REMOVER. My usual ritual is to go around with a stain remover first (like vanish), let it do its job, then wash the carpet with the cleaner. You will need to air the room well when you're done.