how does increasing the number of justices increase the court’s power? I would argue that it lessons each justice’s power.
Also, I'm very pleased that you brought up this topic. A lot of folks are critically thinking about things and trying to come up with solutions.
Hypothetical:
Let's say you want to go from 9 to 15 Justices. Who picks the appointees? The President does. On 2/1/2013, Congress has authorized the SCOTUS to go from 9 to 15 Justices. If Obama is President at the time, he gets to send 6 nominees to be approved by Congress. You know as well as I do that Democrat nominees go through without any issues. If Romney is President, do you believe he will nominate 6 strict constitutionalists? Do you even think it will be 2-3?
So now instead of getting 5-4 and 6-3 decisions it becomes 11-4 and 12-3.
Yes, the individual Justice's power and influence is diminished. BUT how many years and Presidents’ SCOTUS nominees would it take to balance out the SCOTUS? If it could be even be done at that point.
This is all IMHO. I'm not a Constitutional scholar, etc. but just an average guy who loves our Country!