You can just connect the optical or coax digital audio connection on your Blu Ray to the 1400 and leave it at that. There is no reason to connect the audio to the TV. Set the Blu Ray to decode the new lossless codecs to LPCM, since the 1400 does not decode the new codecs.
Your cable box audio should also connect directly the the 1400 with a digital audio connection if you want the TV sound to play through your home theater setup. If you want to also be able to use the TV with its own speakers, e.g. for watching news, you should get that from just the HDMI cable from the cable box to the TV.
Personally, I just use my receiver (also an old 1400) for all the sound.
Your cable box audio should also connect directly the the 1400 with a digital audio connection if you want the TV sound to play through your home theater setup. If you want to also be able to use the TV with its own speakers, e.g. for watching news, you should get that from just the HDMI cable from the cable box to the TV.
Personally, I just use my receiver (also an old 1400) for all the sound.