Like people say, get the transformer. I would suggest though that you buy them (the identical device!) from eBay though for pricing reasons. I have bought two separate 2000W units (one to run a US-model amplifier/receiver and one to run a KitchenAid) and they're about $65 each; see item 270767008656 (I have bought from this seller and recommend them).
In terms of answers to your latest questions, they are:
1) about 1000W* including the modeling lamp
2) no, nor does it have a poor power-factor or high inrush-current, which is what they're really asking
4) irrelevant, since we know the approx total power
5) presumably yes
The power ratings on the transformers are largely thermally limited and aimed for continuous use, while the flashes draw power for only about 1.5s each time you fire them. Therefore you can comfortably run two of the flashes from a single 2000W transformer (it will hum a bit during recycling but will work fine). The transformer would be less-stressed if you bought the 3000W version** but I don't think that is necessary. The transformers have two sockets on the front so you won't need a powerboard; just plug the two flashes in using their original US cords.
If connecting two flashes to the 2000W transformer causes its breaker to pop, you could buy a second 2000W transformer (one for each flash). This is highly unlikely with your higher-quality flashes though, so don't worry yet.
While there is a 240V version of this flash, there will be big differences in how the recycling circuit is setup so it is generally not economic to modify the 110V to work with 240V. Using a transformer is the best option.
* it's a 600J flash with 1.5s recharge (400W output power into the capacitors), but the charging circuit is often only about 70% efficient. Recycling the flash will therefore pull about 500-600W, plus the modelling light is 150W on the 110V version, though there looks to be a 250W option. The expected power consumption is therefore about 750W, so 1000W is a fairly safe/conservative estimate.
** eBay 140670722876 is clearly from the same chinese factory, just larger.
Last edited by polyglot; 04-17-2012 at 04:02 AM. Click to view previous post history.