I have different experience.
With additional warranty say Res Q from Reliance Digital, they have team to do serice part on site, did istallation and demo for me (just demo I would say), even if any problem persist in first year they will do the service part and no need to contact manufacturer - which in most cases won`t be available in all cities (Onkyo has main in Chennai I think, Mumbai also have one but nothing good in Pune). How Res Q manages not my concern but gives bit piece of mind for said perios (I have 3 years totals covered).
APC backup is good no doubt but it only covers the power related thing, HTiB have other most known problem is with HDMI ports.
Additionally, the spares becomes obsolute with newer model coming in, in such cases they compensate the money (happened with me, check my previous posts).
Costwise the extednded warranty ain`t that much if brought bundled initially. Just my thoughts...