Replacing video card in laptop

Welcome. Is the Alienware 17 (A17-6560). Processor - Intel Core i7 4700MQ, graphics card - NVIDIA Geforce GTX 770M 3GB GDDR5(graphics card two integrated and discrete; discrete,according to the manufacturer, is removed, i.e. not soldered to the Mat.Board), chipset Mat. motherboard - Intel HM87 Express. The question is. Need to replace the video card to a more powerful. Is it possible? Support from the manufacturer said that it is possible. Said that it is possible to replace, for example, on the 880M. Some service centers even say that you can replace 1070M(with radiator), but the 880M is impossible, because it does not pass voltage. So what can be replaced? And everyone says different things.