That does look like a decent beginner kit to get some technique down before you upgrade to bigger stuff.
The problem is upgradability and compatibility. That kit comes with 2 24"x24" softboxes and 2 standard reflectors. Those softboxes are definitely a little small, though, for full-length portraits. The possibility of getting larger softboxes that will work with these strobes is hit-or-miss. There are also other modifiers (beauty dishes, etc.) that will probably not be available to fit these strobes. On the other hand, there are plenty of umbrella-style modifiers that should work just fine.
The point is that yes, this will get you a good start in studio lighting without spending much money. But it will also be hard to grow this system. You will end up buying AlienBees, Elinchrom, etc. strobes before too long. Of course, the cost of a single strobe (no modifiers or stands) from any of those other brands is more than the cost of this whole kit with 2 strobes, 2 stands (the stands should work with any other brand of lights, although they might be too lightweight for use with larger modifiers) and 2 softboxes. That's a pretty darn good deal, and if Impact makes speedrings for these lights (which let you attach any 3rd-party softbox to the strobes) then you might be okay.
You ask about the power. 100W/s is good for f/8 at ISO 100. Through the softbox, you usually lose another stop so you will be looking at f/5.6 at ISO 100. This is not terribly powerful. Most studios use monolights in the 250W/s to 500W/s range. I have a few AlienBees B800's (320W/s) which easily get me f/13 bare, or f/10-f/11 through my softboxes. This is generally the f-stop range that studio photographers shoot for (no pun intended). Of course, you can set your camera body to ISO 200 or ISO 400 and achieve the same lens f-stops with lower powered lights. I'm not really sure why everybody shoots at ISO 100, but most studio lights are so powerful that you almost have to. If you have multiple lights in a small area with a light colored background then you might even have to step down to ISO 50 to avoid shooting at f/22 or something.
I don't know.... if I were outfitting a whole room for dedicated studio use, I wouldn't skimp on the lights. I would at least go for AlienBees or Elinchrom (I own 2 AlienBees myself) if not for something even spendier like Profoto. 400sf is a lot of space (i.e., money) to dedicate to photography.
As far as "taking it with you", most monolights are fairly reasonably sized. AlienBees are about the most power per size you can get, but these don't look much bigger. The problem is powering it once you get there. You will need a power source... of course a wall socket is idea, but AlienBees also sells a $300 system called the Vagabond which is basically a big battery with a high-dollar inverter (cheap car inverters don't output the right kind of current for powering most lights... they need pure sine wave current, while most inverters create square wave current). However, no matter what system you end up with, your biggest pain will be the stands, softboxes and other modifiers. Unfortunately there is no way to make these terribly compact. The kit that you linked has a nice carrying system... 8' light stands can usually collapse pretty tiny. I've got an 8' Impact light stand myself. It collapses very small, but it bends visibly when I raise it up with a big softbox (32"x40") on it and I have to worry about it tipping over (the footprint doesn't get big enough to really support larger modifiers). However, I still like it for its compactness.
One starter kit that is somewhat more expensive but seems a little better supported from the manufacturer is Calumet Genesis. I would look into those as well. I would also take a look at this series of videos from ProPhotoLife. They are extremely helpful and I still use them for reference and inspiration when I try something new in the studio.
http://www.youtube.com/user/prophotolife#p/u/32/EQBVSGBBiNk
You will see in these videos how much you can do with even just cheap desk lamp type lighting and some acetate panels (or white ripstop nylon from the fabric store as a substitute). If you are just doing product shots then this is really all you need, as long as you have a good tripod for relatively long exposures.