I think that while it's a given that everyone is different in terms of how much of anything they can tolerate, taking the following into account:
-Recovery variables (diet, sleep patterns etc)
-How strenuous and how much 'other' work you must recovery from each day (weight training, sports, etc)
-How much of an effect cardio has during a prep (some people get more of a bang from just small amounts)
I still believe that you'd need a serious amount to hamper muscular gains. Sure you may have certain trainers who's recovery may be so horrible that it can be an issue, but more often than not, I think it's something you can offset with better dietary approaches.
Some coaches will even tell you that added LISS work (or any type of energy system work) will actually improve nutgrient delivery and contribute to muscle gain in the off season.
On a slight tangent, you have the two schools of thought about off season cardio affecting how much of a response you get when you need to use cardio in a prep. One school believes that by having some type of cardio year round, your system is just more efficient in every manner. The other school believes that by not getting used to any cardio in the off season, your body will give a more pronounced responsed when you have to rely on it when cutting.
As to the AAS in the equation,... well, I think most people would agree that it does change things a bit.