I'm considering the same Yamaha models. I've looked at HK too.
Silly Q tho, if you are considering HK equivalent model then is the HK 347 the correct choice? Isnt the HK 252 more like the 2 Yamaha models? From what I've read I believe the 347 is an older model which is more on par with the Yamaha 6080. afaik the 347 doesnt do Dolby HD or DTS HD but the 254 does.