According to the HK web site, the PA 5800 is 5x80@8 ohms. Given that it is about then years old, it is probably a classic HK amp design that would mate very well with a 970 if you are only going with a 5.1 system.

With so much in transition, a 970/5800 combo isn't such a bad idea -- you give up the smaller space of going to a 1070, but you retain the flexibility to switch to something newer in a year or two. On the other hand, though it has a bit less power (albeit with 7 channels instead of 5), the 1070 should be very close, if not equal to the 5800 in almost any situation since it is rare that you'll have something in all seven channels at the same time.

Either way, you get the same basic feature set, and that's a winner.