Bus width is a concern mostly for future generations, currently the clock speed is fast to provide adequate bandwidth.
This is the follow up article
To make the 4GB of VRAM on the GTX 670 work for you, you are going to need at least three of them for 3-way SLI, to give you the performance to back up the VRAM. Or, we would also like to see 4GB of VRAM on 2-way GTX 680 overclocked, or even 3-way GTX 680. There are advantages to more VRAM, and 4GB can smooth out performance in a lot of games, but today's games are more GPU demanding than ever. These newer games require a lot of performance, and GTX 670 is already starting to show its age in today's latest games. We are already experiencing today the fact that we need faster GPUs in games like Far Cry 3 and Hitman: Absolution.
3 GPUs or the VRAM isn't worth it unfortunately. You also need enough resolution to make that performance worthwhile to have, which is beyond 2560x1600 and 3x1080p surround
Now that you have this insight, if you want a laugh: http://www.newegg.com/Product/Product.aspx?Item=N82E16814127684