If you're happy with the Holley, I'd stick with it.
Around here, Demons bring exactly nothing on the used market, but you can sell a good used holley for $200-$300.
For street, you'll like the air gap a lot better. If you want a more fuel efficient carb, I highly recommend a Holley street avenger. I run a 750 Quickfuel double pumper in racing season and a 670 vac. sec. street avenger the rest of the time. Its great. Great throttle response, electric choke, good mileage.
My double pumper is .15 quicker on average, but with the SA I still have to take timing out and put weight in to slow it down to 12.00....so it will support some horsepower.
