Regarding the dip in response, are you referring to Danny Richie of GR Research? The consensus here is that he should do more research. I watched him invert a horn after removing it - did he fix it before measuring? ¯\_(ツ)_/¯
RF-7 iii is a much larger speaker than the 8000 and a significant step up.
Heritage has a dedicated midrange driver/horn, and a more complex network. Stay with Heritage If you are pursuing accuracy.
If you want to shake the house, get the RF-7iii’s.