[AnthonyG]

If you're budget is $4000 (assumption from the links you posted) you should be able to get a really good used US unit for that price, or with a bit of shopping around you should be able to find a new Gen 2+ with specs better than what you've linked too. I highly encourage you to do some research and ask questions.

The thing with purchasing through airsoft/retail stores is that they don't provide any guarantee of what you are actually getting. They say things like "up to 1000 FOM" or "1600-1800 FOM", but in reality you need more information to make an informed purchase. 1000 FOM doesn't tell you much. It's kind of like selling a vehicle on the premise of "horsepower" alone; it will give you a good idea of how powerful the vehicle is, but it doesn't tell you what it is capable of; is it a pickup-truck, a sedan, or a sports car? Yes, horsepower matters, but so does the number of cylinders, the height of your wheelbase, and your trunk capacity...

It actually astounds me that companies like GSCI can get away with selling "mystery" tubes to customers at such ridiculous prices. I still have yet to find another industry where that kind of behavior is an acceptable practice.