Well that's weird. Why do you want to 'underclock' your 1700+ to 1.1GHz?
50oC? You're kidding aren't you?!!
Changing PSU helps.... I changed mine from 230W to 300W, and I realised that my system is more stable.....
As for heat, I don't install any system fans, and I don't overclock more importantly, but i get around 20-30 degrees C on idle..... ^_^
If I'd to run it on full usage..... then it'll be hot.
Specs:
AMD 1.2Ghz Athlon with Taisol Fan.
300W PSU (don't know what's the name.....just changed it recently heh)
And a piece of advice:
Don't overclock your graphics card too much
And oh..... my system could only achieve that 20 degrees on idle cuz I leave my casing open.