The motherboard would not be the issue - it would be the case.
I don't know what you mean by double-width. There's two things that could mean:
1 - Regular profile vs low profile. Regular profile is a normal width expansion card, and low-profile is half-width, in terms of how wide the slot itself is in the back of the case
2 - Single-slot vs double-slot - a double slot means that if there were another PCIe or similar slot in the motherboard next to the one you're putting your graphics card in, a double-slot card, while it may or may not take up two slots on the back plates, would obstruct the next slot on the motherboard.
Without seeing your case, your motherboard, and the specific GT 730 you're using, this is not a question that can be answered.