Some members here with HCH's (tbaleno specifically, I think?) have massively upgraded their stereos, and it does affect their vehicles to some degree- the engine has to regen more frequently to keep the 12V charged.

But its certainly no more of a 'strain' on the system than any other car. The motor/generator is really a very large alternator- so I don't see an issue. It's not like the HAH doesn't have the oomph to keep it and a big stereo load going.