Not JC, but will answer the question

For True HD and DTS MA, you need to use LPCM. You can use LPCM for everything if your receiver can accept it, the player will just do all the decoding. This is what I do. If you must see "DTS" or "DDII" on your receiver, you'll need to switch to bitstream when not using a True HD or DTS MA disc. Remember, this is with HDMI. I think the bitstream answer JC gave is in regards to a digital coax or optical connection.
Pat
EDIT: I See you have the 661 as well, just leave the PS3 on LPCM and there will be no need to worry. You'll get everything. If you want to see what is being output, hit the display button on the PS3 remote.