A couple of things:
First, all Echo1 guns are made overseas. Most are made in China, though the Platinum series is made in Taiwan as far as I know. Echo1 and Echo1 USA are the same company, one name is just shorter to type. There is no quality difference between the two, as every single Echo1 gun IS an Echo1 USA gun. Long name or shorter, but they're the same.
Second, I would recommend against attempting to make the MTC-3 into a 'sniper rifle'. There are a couple of reasons.
1) Less precise OEM means that it takes a lot more work, hand fitting parts, and buying more parts to make it shoot well. A more precise gun out of the box yields better results.
2) A longer barrel usually yields better accuracy (to a point). Attempting to extend the handguard and barrel on this model will probably not give you the results you want.
3) Most 'sniper rifles' are going to be bolt action, as they have a higher FPS limit. You can qualify for a DMR class if you make the AEG semi-auto-only, but that's a lower FPS than the bolt action.
Echo1 USA makes decent guns, but they're not going to be the precision machine you're dreaming of. I would check G&G, KWA, and VFC if you want a more accurate AEG. Additionally, the MTC-3 is an odd AEG. It uses the shortest barrel in the MTC series, but has a bulky, heavy stock that is not adjustable. The MTC-2 has a longer barrel, and is a lighter AEG with an adjustable stock. I would check it out if you like that series.
It's available
here at Airsoft Outlet NW. They have better service than Airsplat, and any Echo1 gun should be the same price at either store, but AONW will check to make sure the gun works and help you with the warranty, if it ends up you do need to use it.
I would just buckle down and admit that you're going to need two rifles. One, a less expensive assault rifle to start out with, start learning the ropes, and get some experience. Two, once you know what you want, look for a more expensive, more precise rifle, either in a DMR or bolt action setup.
Spitfire is on with some info, but there's more to it. First, consider the FPS rules where you'll be playing. Many fields don't allow anything full-auto over 400FPS. Second, to make an electric gun over 450FPS often means extra stress on the internals, which can result in increased weapon failures. That can be expensive, especially for younger players.
He's right that with most AEGs, the only way to change the velocity is with a spring change. Unlike paintball, there is no quick adjustment to change muzzle velocity. Some guns do have a quick change spring, but it almost always takes at least a small amount of disassembly.