Capital Expenditures to Increase Rent

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I'm currently comparing two 4-plex units. Each unit contains 2 bedroom and 1 bath units and are comparable in square footage. Property A is in a better location, older, slightly outdated, and each unit is renting out for approx. $525 per unit. Property B is slight out of town, very new, units are much nicer, and each unit is renting out for $675 per unit. Average rent for a two bedroom apartment is about $600 a month. 

What are the most cost effective capital expenditures that you have done to increase rent? 

Things I'm considering implementing are minor kitchen updates, minor bathroom updates, and laying hardwood floors. 

Anyone have any thoughts? Anything that I'm not considering?