The best approach is to increase the efficiency through science and let the technology naturally be adopted like every other innovation that wins in the marketplace. I'm still for the cap, but if that is the linchpin for adoption to take hold widespread, something must be wrong with the product.
Note also that an increase in the price of energy causes prices across the board for every manufactured item to increase. Classic inflation, 1970s style. This is not the best economic environment to cause inflation in.
Consider house-top installations. If each only produces 100 watts, the cost of the inverter and utility hookup will make it untenable even if the panels are free. (Inverter cost/watt goes down pretty fast with capacity and most of the hookup cost is independent of the capacity.)
There's also a huge psychological boost in being able to be energy neutral.
Silicon isn't the only cost. As I wrote, inefficient technology makes small systems uneconomic.
FWIW, the systems with the highest efficiency right now actually have less silicon than typical rooftop systems.
Note also that there is no one "cost of silicon" - silicon prices vary widely. Many of the low-silicon cost/efficiency systems actually use more silicon than some of the high-cost/high-efficiency systems.
The key statistic is being able to calculate when solar is cost competitive with coal, because once you hit that point it will start showing up everywhere. Of course this depends on where you live, because different regions of the country A) receive differing amounts of sunlight B) pay differing rates for the amount of electricity generated. If you're talking about an area like LA where there is a lot of sunlight and electricity costs a lot, solar is already probably cheaper than coal. In Fairbanks, AK on the other hand it will take a bit longer.
Another key to getting solar to be cheaper than coal is implementing real-time pricing. To quote again,
"Though solar power is generally judged on the basis of whether it can beat the retail price of coal-generated electricity, the comparison is in some ways misleading. The true value of solar power lies in the fact that it is most productive when the weather is sunny and hot-- precisely when consumer demand forces a utility to operate at full throttle. According to PG&E, peak demand is growing 25 percent faster than overall electricity needs, but the last quarter of capacity is needed less than ten percent of the time. 'Peak shaving' with electricity produced by rooftop solar panels relieves that pressure on utilities, damping the prime driver to build new gas-fired plants. It also reduces costs. Utilities "turn on" power plants in order of their variable cost, often called "dispatch cost," starting with the least expensive plant to operate and moving to the most expensive as demand rises. Solar installations produce electricity at virtually no extra cost at just the same time when units with very high variable costs are called upon to run. By displacing these high-variable-cost units, solar units can provide tremendous savings for the utility and the consumer-- and the atmosphere."
"To date, however, most owners of solar photovoltaic systems owners do not get the discount they deserve on their electric bills. Typically, utilities charge customers using a weighted average of the cost of generating electricity over the course of a day. Some jurisdictions are now experimenting with a different rate structure-- 'real time pricing'-- charging customers hour by hour for the true cost of the electricity they use, and thus allowing them to reap the full value of avoiding the cost of peak power on the grid."
"Given all that, almost everyone in the industry agrees that when the price per peak watt falls to $1 and the storage problem is solved, solar-generated electricity will compete with coal-fired electricity virtually everywhere." (p. 19)