Let me jump in. I'm not sure where double current comes from. I would think that when whole 0.1556A of bias current flows thru the speaker then the other transistor has to be off (Il=Ip-In).
You cannot calculate RMS because you don't know the shape (1.41x relationship applies only to sinewave).
Number of watts before jumping to class B might be not so important. Main purpose of bias is to avoid switchover distortion and not the nonlinearities of transistors. Increasing bias current increases distortion (overbias) since it is also increasing area of double transconductance (gm doubling) where gain is doubled since both transistors conduct. Of course emitter resistors can be set to minimize it but tests showed (Douglas Self) that increasing bias increases distortion. Problem is that holding amplifier on the edge of class B (minimum bias to make both transistors conduct) is difficult to do. I'm not sure what happens when bias is set much higher, but not pure class A.
read page 138-140:
http://books.google.com/books?id=Qpmi4ia2nhcC&pg=PA140&lpg=PA140&dq=Douglas+Self+class+b+overbias&source=bl&ots=hAE7f6LFUj&sig=MTAeHQeKHRn17SEEUnMv03DQprg&hl=en&ei=ORDJTLSBK8rOnAfWz7XhDw&sa=X&oi=book_result&ct=result&resnum=6&sqi=2&ved=0CCwQ6AEwBQ#v=onepage&q&f=false
You cannot calculate RMS because you don't know the shape (1.41x relationship applies only to sinewave).
Number of watts before jumping to class B might be not so important. Main purpose of bias is to avoid switchover distortion and not the nonlinearities of transistors. Increasing bias current increases distortion (overbias) since it is also increasing area of double transconductance (gm doubling) where gain is doubled since both transistors conduct. Of course emitter resistors can be set to minimize it but tests showed (Douglas Self) that increasing bias increases distortion. Problem is that holding amplifier on the edge of class B (minimum bias to make both transistors conduct) is difficult to do. I'm not sure what happens when bias is set much higher, but not pure class A.
read page 138-140:
http://books.google.com/books?id=Qpmi4ia2nhcC&pg=PA140&lpg=PA140&dq=Douglas+Self+class+b+overbias&source=bl&ots=hAE7f6LFUj&sig=MTAeHQeKHRn17SEEUnMv03DQprg&hl=en&ei=ORDJTLSBK8rOnAfWz7XhDw&sa=X&oi=book_result&ct=result&resnum=6&sqi=2&ved=0CCwQ6AEwBQ#v=onepage&q&f=false