Do you need a 1.3a spec HDMI cable if you want Dolby TrueHD sound from your receiver? I have a 1.3a receiver.

Or will any HDMI cable(like those from monoprice) be ok?

For shorter lengths, any good cable will do. I would say that if you were going to run lengths of 15' or more, then look into 1.3a HDMI cables.

No! You don't have to have 1.3a to take advantage of DTHD. HDMI is backward compatable so if your have decoder connected with 1.2 to your source (HD DVD) that can send the DTHD in bitrate format to that decoder, you will be get DTHD sound. However! 1.3a is required for Deep Color and xvYCC but only if your display device is capable of accepting it.

By HDMI 1.3a cables do we mean Category 1 or Category 2 or none at all?

Why is it that HDMI 1.3a cables are required for Deep Color, etc?

I had always thought that so long as the TV and the source are HDMI 1.3a any ol' HDMI cable will do?

HDMi 1.3a can have a higher bandwidth. certified 1.3a cables have been tested to pass that. 1.2 and lower cables might work or might not.

Gotcha.