You are correct. The latest formats of Dolby Digital and DTS are distorted and I have to switch to the PCM Downmix. I have done my best to skirt similar issues by running an HDMI cable to the TV for video and either an optical or digital cable to the receiver for video. Additionally, the 555ES doesn't have multi-zone capability, so I had to get creative to power speakers in the kitchen, living room, and on the deck. Basically I had to build two separate systems. The 555 runs 5.1 in the media room and then I have a cheaper Sony receiver hidden below running to a speaker selector. The two receivers operate separately, but audio components are connected to both through optical splitters, so music can be played through all speakers from the same source (generally through home sharing on the Apple TV). I am realizing how ridiculous this is as I type it. But it works, works pretty well, and I have been happy with it. I guess one huge advantage to the Yamaha is I would really only have one HDMI cable running up to the TV. That and the ability to handle newer audio formats.
That said, is the 800 one of the better deals out there for the price?
Yamaha often is the best deal going. I have very little brand loyalty, but the last two times I have purchased a receiver for my home theater, they have been Yamaha. There have been times when, if I had been looking for a receiver, I would have ended up with a Marantz or Denon, but there is no reason to reject Yamaha.
No matter what brand you buy, I recommend buying from an authorized dealer, just in case something goes wrong. Often, the best deals are on recently discontinued items, which describes both of my most recent home theater receiver purchases.
The RX-A800 is at a good level, not so low that it is a cheap piece of junk, and not so high that one is wasting too much money, if one is getting it at a reasonable price. I would only go with a higher model if I needed a feature it lacked, or the price on the higher model was too good to pass up. I would also consider the RX-A700, unless it lacked a feature I required.
I was running a $600 receiver with speakers over $6k, and it sounded great (as it should). Because I wanted more features, I replaced it with a receiver that retails for about $1700. Unless I engage a feature that affects the sound, it sounds the same as the $600 receiver. If my speakers were more difficult to drive, it could have made a difference, as it can put out about twice as much power as the cheaper receiver, but the old receiver could drive my speakers to painful levels with crystal clarity, so the extra power is useless for me. Basically, once you get a decent receiver, a higher model gives you more features and more power, not anything else. So, many times, a higher model is just a waste of money. (I got mine for less than $500; I would really be kicking myself if I had wasted $1700 on it.)
If you require more power than a moderate level receiver, it is usually best to get a receiver with preamp outputs for all channels and get a separate power amplifier(s), as one can get more power that way than with a high end receiver.
So basically, you probably want to go with the cheapest receiver from a good brand that has all of the features you require (now and in the near future). And that extra money should go into the speaker fund (keeping in mind that subwoofers are speakers, too). That is, assuming you want the best sound per dollar spent. Most people, though, put too much of their money in receivers and other electronics and not enough into their speakers, as it is easy to see that more power is better and more features is better, but it is harder for people to see better sound quality in a speaker.