Chargers - where is my maths/understandiing wrong?

[snappy]

Hi, Read extensively to try and understand battery handling/charging, especially on this site.
I have a 4s 5400mah battery. I'm looking for a charger.
If I understand it correctly then at 1C I need 5.4amps or more from a charger, and using watts=voltsxamps, for a 1c charge rate I need over 90watts from the charger. Is this right?
Looking at the commentary on a Venom Pro Duo X2 80w, with a charge rate up to 7amps, they claim 25minutes to charge a 4s 5500 lipo. Is it a charger that is really 160watts because its an X2 - and then only if charging one lipo?
And if I'm right in my maths, should I be looking for 100watts or more given in time higher mah batts will probably be used, or 6s?
What is the optimum power parameters to use?

 

[AeroJ]

You don't have to charge at 5.4 amps, that is just the maximum charge rate that pack can take for (in theory) the fastest charge cycle.
Any balance charger that can do up to 5 amps will be fine. I charge my 4S LiPos on a standard B6 type charger, which can do up to 5.5 amp charge rate, which are only £30 or so. However I still only charge at 3 to 5 amps because I don't want to stress my packs by always ramming them full with the maximum possible...