I see. Perhaps we got a bit confused by the x1.4 thing.
Strictly, Watts = V*A*Pf. The trouble being that (especially) with consumer equipment, you don't know what the power factor (Pf) is. You are then faced with the prospect of trying to find it out (from the manufacturer or by measurement) or making an assumption. The assumption you make depends on what sort of equipment it is (inductive loads are bad for Pf) and if it has any kind of PFC (power factor correction) circuitry. Ideally, Pf = 1 (Watts = V*A*1) but it can vary widely.
But that has nothing to do with your x1.4.
When APC are telling you to multiply DC power by 1.4, they are in fact trying to make a (probably fair) assumption that your AC/DC PSU is about 60% efficient (i.e. it 'wastes' 40% of the power it consumes as heat etc.).
This assumption probably errs on the side of caution (assumes that your PSU is fully-loaded) which might give you a larger UPS than you actually need (but larger = longer endurance = good). My rule-of-thumb is, as I said, to use the power rating on the equipment plate. Often a PSU has input AC Amps/Volts written on it.
Just as a note, on the APC website there is a UPS sizer that apparently uses measured data from a variety of equipment to suggest a UPS. They also have an Express Selector version that allows you to enter power requirements directly in Watts, VA, kVA or Amps. Give it a try and see what it comes up with.
Hope this clears things up a bit.