Paul Allen is on a quest to expand access to space. Stratolaunch is envisioned as a reusable CTOL air-launch platform with a 550,000 pound payload capacity. With reduced launch wait times, launch location flexibility, and more missions per year, this innovative platform should start to bend the launch cost curve earthward. That’s good news for the development and deployment of space-based solar power.
Visit the Stratolaunch website for more information.
Citizens for Space Based Solar Power 
I am not so sure that Paul Allen’s StratoLaunch will directly help reduce the cost of hauling power satellite parts into orbit, but it is essential for another reason. *IF* we build the single stage to orbit Skylon, it is the ideal ferry vehicle to move those things from the factories to the equatorial runways.
Assuming they are built by Airbus and Boeing, they could self-ferry from the plants where they are made, but the local authorities are not going to let them take off. The noise would be intollerable.
It would take slight modification, the landing gear would need to be lengthened a little, but otherwise, a Skylon would fit nicely on a StratoLaunch plane. There is an outline drawing here http://htyp.org/design_to_cost