i have a stealth fan in my gf's computer (a vantec 60mm stealth to be exact) and it wasn't very stealthy....kinda loud actually and definitely not the 21dba it advertises thought it does blow pretty strong. i've read similar things about the 80mm stealth on newegg's feedback/reviews. I'm sure it'll be an improvement over your existing one though.
A thermalright heatsink + a Panaflo might be a better cooling and quieter combination.
www.svc.com is the place to go.
46C isn't anything to be worried about. My Tbird 1.1ghz ran at 46C in the winter time and 50C in the summer time (at idle), and I had no problems with it. At load would bring me up to 53-55C, still not a problem. Tbirds tend to be quite hot....now with my 1800 tbred, i get idle of 39-40C and oc'd to 1733mhz, it's only at 41C; using the same heatsink too. Unless you're experiencing lock-ups, weird problems...etc, don't be worried.
SVC link