As mentioned above you might have to qualify for the new house payment without being able to use any offsetting rental income from your current home. Since you do have a history of renting and managing the duplex you might find a lender that will accept a lease and count 75% of the rental amount to offset the mortgage.
I understand where msot responders feel that you should sell and buy something cheaper with possible better cash flow as most of the home we live in ourselves our not the ideal properties for cash flow. While I agree you can look at if from the perspective of could you buy less expensive better cash flowing properties that would produce better roi and you might be able to and for some that might be the best thing to do. One thing you have to factor in if thinking of doing that is the cost of selling (realtor commissions and closing costs) and the costs of buying (closing costs and possibly higher interest rates since your new houses your will replace this one with will have to be done as rentals) and really net out what your goals are.
You would also want to consider what you feel the appreciation potential is if you find that important as well as the ease of renting. Maybe you feel more comfortable renting your current house and the types of renters you will get there than lower income/highr roi properties.
I think these are all factors that only you can fully decide what is best for you.