I bought the 521 a week ago.
I ordered an Onkyo 608 to replace it. The 608 is a little bit more money, but I get analog -> HDMI upconversion, extra output channels (7.1 vs 5.1) more power, dedicated amps, and a much better OSD that also works over HDMI (as opposed to just component like the Pio).
I almost got the Yamaha 567 (same features listed above, but a weaker amp section) for $229 from Best Buy. I got the 608 from A4L for $279.