Acceptable hiss ?

With your ear up against the tweeter you're going to hear some hiss. If it's the same in both channels so much the better. It's normal. As long as it doesn't intrude at your listening position don't worry about it.

with a high quality pre and amp, you should hear virtually no hiss, even with your ear pressed close to the tweeter with volumn set at your "normal" listening point. this is particularly true of line stages but equally so for the very best phono stages.

I would say, due all respect, it is normal for a receiver. I don't know much about your receiver, but it is common for those digital receivers to have relatively high noise floor. Try "direct" mode if available, and let me know what happens when you connect rear speakers to front terminals of the amp.

I hear it if my ear is 12 inches or closer...

Justy, try to determine whether it is from the receiver. Connect right/left speakers to rear terminals, etc. If the noise comes from the same speakers, then, it's speakers or cable (or signal interference). But it is still possible in your case that it is normal, although I don't know how close your ear is when you hear hiss. In HT setting, you usually set the front two speakers louder than rears. That may be why you hear louder hiss from fronts. Anyways, in my case it was receiver and I think it's the prime suspect. BTW, If I don't hear it from listening position, I would not mind.

The hiss is louder from the left and right channels than is is from the center/rears. I have Linn Lk400 (dont ask) 6ft biwire cables going to the Left/Right; and custom made cables going to center/rear. The Linn cables are about 8 years old, could this be an issue ?

I have tubes.If I hear any hiss,I got tube problems. Not sure how it goes for SS eqpt. Is the hiss equal for both speakers? All 5 speakers? By the way,nice speaker choice!