gdgt

I'm not entirely sure about the build quality - reports vary, but it would seem to me that the ASUS ROG notebooks might be up your street. The only thing is that if you're looking for significant GPU power, then a certain degree of boat-anchorness is inevitable. The G53Sw is 3.6Kg for example, i.e. equivalent to many other companies 17-inch offerings (But you can get a full HD panel in this 15-incher) - and oddly, the G73Sw is not much heavier. But the price is right - Newegg's prices seem to be in your ballpark.

I doubt you would want to look into it as it's very likely to be far north of your budget, but the forthcoming Sony Z replacement appears to have a Thunderbolt-based external GPU as an adjunct to a super-thin-and-light (with Intel graphics built in).

However if you want something that's genuinely light - then you're going to have to compromise. The M11x appears to be about the only system which could remotely meet your needs, but I doubt the 540M will deal with particularly demanding games and 2Kg is still a heavy machine (at least, by my yardsticks). But in the end, it might be the only logical choice if it has to be one machine - I certainly can't imagine lugging around >3.5Kgs on anywhere near a regular basis.

Another alternative is to not excessively compromise to get everything into one box, and invest in a desktop (or something like a G73 as a DTR) that you can do full-blown development on, and also a <1.5Kg CULV for your actually portable needs - assuming you won't be developing games everywhere you actually travel.