The AV8802a supports Dolby Atmos out of the box will support DTS:X with a free firmware upgrade. Auro-3D is available for $199. Since you're only running a 5 channel system, I'm not sure how important these are for you. I'm only running 5.1 and will probably stay that way for a long time (I didn't jump on the 11 channel bandwagon -- preferring to focus on sound quality instead). I would rather have a 5.1 system that sounds ultra realistic than an 11 channel special effects system that sounds okay.
In the end, I suppose it comes down to budget. I would say buy the best you can afford or are willing to spend. Since you ran your last system for 20 years, you will probably have this new processor for at least 10 more years!
Keep us informed on what you finally decide and how it works out. Keep in mind that you should burn in the unit 100-200 hours before making final judgement (if you buy it new).