Hi,
I have a 5800 presently that I have had upgraded to approx 95% of a 5803 when they offered it 2 years ago. Apparantly there will be a catchup upgrade offered again in the next year or so.
Upgraded or not the 5800 has 7 170w amps which will allow you to get the most out of almost any set of speakers without straining. I run 9 speakers in my HT and 5 are 4ohm with a sensitivity of 87. The 5800 doesn't show a sign of strain.
If you ever decide that dvd-a and sacd are of interest you can pickup a couple of old mltidisk players because the 5800 is the only reciever from that time with 2 sets of 8ch analogs.
Anyway it's the last one I'll ever need and I love it. If you could get a 5803 cheaply now that the 5805 is out, I'd wait for that insted of the upgrade route because it adds video upconverting.
Peter m.
