Actually, your Coolermaster 450W 24Pin choice is just fine, because it obviously will be compatible with the board and it has Active Power Factor Correction as well. That is definitely a solid choice, and your heatsink choice isn't a bad one either. I have heard the Silent Boost K8 and it is very quiet, mainly being that it's hydro-wave bearing fan spins only at roughly2450-2500rpms. I think the other guy must be mistaking it for the other Thermaltake K8 fan that really does sound like a jet engine, because there is no way that thing could reach that noise level.
If you want better cooling but don't want to (and don't have to either) spent $40 for just a Thermalright heatsink, then I would suggest the Zalman CNPS7000B-AlCu or the all-copper CNPS7000B-Cu. However, if you are going to bump it up to the 250Mhz or so you specify, I would be more inclined to go with a Panaflo fan and a Thermalright XP-90 or XP-120. They have excellent cooling, and are surprisingly light.