Do you have any truoble with the remote controls like changing channels on the wrong box or are they different? I have the Coolsat 5000 now and I am thinking about upgrading to HD.
They are different IR codesets. I have a 8100 & 6000 stacked and have never had any issues with the two remotes interfering. I've also used them with a Slingbox and it had not trouble controlling them separately as well.