I'm relatively a novice in the world of AVR, but having recently demo'd a whole load of AVR's I can tell you the 3020 will easily handly your RX8 av12. I demo'd and ended up buying a 2020, which I demo'd with RX6's, RX8's, B&W 683 plus others. The 2020 handled these with ease, so this should be a breeze in the park for the 3020. One thing I would say is go demo it yourself, also try the Pioneer SC-LX86 as that's also a great AVR. I'd demo all 4 if you can and decide for yourself. If you can find yourself a copy of March WHF they tested the following
Denon AVR-4520.........4 Stars
Onkyo TX-NR3010.......4 Stars
Pioneer SC-LX86.........5 Stars
Yamaha RX-A3020......5 Stars and the winner of the test
Hope this is of help