Just upgraded my Onkyo SR508 to NR609 in August of 11'. Now I am jonesin for a NR709 because of the better Audyssey in the 709. Is the 709 that much better than the 609? Just upgraded my sub from a Polk PSW10 to a PSW505 in Oct 11'. Now I read how great these HSU subs are and now I kinda would like one of those. Geez....maybe I need to quit reading on the forum so much . Got these beats solo hd headphones and then I had to have the grados SR 60s for 1/3 the cost of the beats. Sometimes I think I hate the hobby I love so much. Will this desire to upgrade ever go away or does even the most highest end of audiophiles always desire something better?
With your desire for better quality bass, you would most likely benefit by upgrading to the 709 which in addition to having more speaker filters in Audyssey MultEQ XT, is also able to EQ the sub, whereas the 609 (2EQ) is not able to EQ the sub.
I feel like the desire to upgrade continues until you hit that first upgrade that falls below the "value curve". In the early stages, each upgrade usually gives appreciable results. But at some point, the payoff starts to diminish. We all draw that line at different points.