Kitchen sinks can vary by as much as 10", and then a garbage disposal can vary by 2-3" or so. Walk into a store and ask for a pair of shoes...average size. likely to be too big (you can still wear them, but they might fall off!), or be too small to actually get on...same idea with average for a kitchen. Some faucets come with attached hoses, some don't, and those that do can vary in length by 6" or so. Nothing worse than having the thing 1/4" too short. Having it 10" too long isn't the best either, but it will work. You want the shutoff valves where you can actually reach them, but still allow the hoses to reach, not back behind the sink where you can't see them to work on it or attach things. When it comes to the drain, water doesn't run uphill, so your wife loves the sink that is even 1/2" deeper than you planned...it might not drain. There are limits on the maximum height as well. Pick an average, and you may end up being stuck with something you don't want because it won't drain, or you can't reach the supply lines.