Motor choice

I have been working with both stepper motors and dc brushed motors and have yet to find a satisfactory solution to the application I desire. I am making specialized rotating tables for video projection using a mercury rotating contact to deliver power to a media player and video projector. I have driven these tables with a stepper motor that is rated at 60 oz/in but have been running into problems at super slow speeds, say .25 rpm to .5 rpm. The stepper motors tend to amplify the stepping at really slow speeds and causes the rotation to be choppy, though I have come close to desirable effect when using a adafruit motor shield and running the commands in the INTERLEAVE setting. It is still a it choppy though. I was using dc brushed motors, but there are restrictions as to what range of speeds can be covered, ideally I would like to be able to go from .5 rpm to 5 rpms but to get a motor with enough torque and these speed characteristics, I have to have special motors made with specific gear box reductions and it gets prohibitive cost wise. Does anyone have a suggestion as to other types of motors that might be useful? I am trying to stay dc, and in the end we want to interface with max in order to scale frame rate to motor speed, in effect speeding up and slowing down the platform according to the frame rate (fps) of the video. I am mostly hardware inclined but do a little programming and am working with someone who can deal with the specifics of the speed translations within max. SO motors and arduino plus shield-Servos?DC Brushless? Something I don't know about? Any suggestions would be great.

Have you tried microstepping your stepper motors at the low speed? Or even reduce the power/amperage you put in the coils, so the steps are less harsh?

yes I have, in fact, the INTERLEAVE command gave me smoother motion then the MICROSTEPPING one. When it goes at such a slow speed, any steps are apparent unfortunately. I need a bit of torque to get the turntable started, it is loaded with a projector and a mac mini, plus power supply and some extra electronics.

Not trying to direct drive am using timing belts. I need this thing to be super quiet, something I failed to mention the first time. I am using it in a gallery setting and any noise from the gearbox is a problem, the last setup I used had to be encased in an aluminum box and I used neoprene to line the walls and isolate the base of the box from the mount platform. i fear these might be a bit noisy but I could be wrong, and I wonder what speed reduction I could get from the 4.5. If it is any more then a 10:1 ratio on the motors speed, the brushes will start to deposit carbon on the motor and short it out.