Following is the scenario.I am currently working for company A right now.

Company A - Non-Profit holding my cap-exempt visa.
Company B - Profit company want to hire me and file my visa under master quota cap on april 1,2010
but that will active on oct 1,2010 I guess.so

Q.1 can I start for working company B right away or before oct 1,2010 any option?
If not then what could be the option

Concurrent h1-b work for company A and Company B or
go to h-1b(cap exempt) to f-1 and comback again on h1-b(quota) on oct 1

can you expain me what could be best option for me here? or any other option