In this paper, we briefly review the ''dynamo'' and ''geomagnetic precursor'' methods of long-term solar activity forecasting. These methods depend upon the most basic aspect of dynamo theory to predict future activity, future magnetic field arises directly from the magnification of pre-existing magnetic field. We then generalize the dynamo technique, allowing the method to be used at any phase of the solar cycle, through the development of the ''Solar Dynamo Amplitude'' (SODA) index. This index is sensitive to the magnetic flux trapped within the Sun's convection zone but insensitive to the phase of the solar cycle. Since magnetic fields inside the Sun can become buoyant, one may think of the acronym SODA as describing the amount of buoyant flux. Using the present value of the SODA index we estimate that the next cycle's smoothed peak activity will be about 210¿30 solar flux units for the 10.7 cm radio flux and a sunspot number of 170¿25. This suggests that solar cycle ♯23 will be large, comparable to cycle ♯22. The estimated peak is expected to occur near 1999.7¿1 year. Since the current approach is novel (using data prior to solar minimum), these estimates may improve when the upcoming solar minimum is reached.