I've done tons of A/B'ing of different Dithering/Resampling schemes on my home system, and my FAVORITES, are the iZotope 64-Bit SRC[Sample Rate Converter], at its HIGHEST settings, along with iZotope MBIT+ Dither at Ultra/High settings, which are BOTH in SoundForge 10/11! I also love the WaveLab Crystal Resampler, but the iZotope 64-Bit SRC sounds a tad more natural to me! But R8Brain is also a good/free resampling software. I've never used Audacity, but I'm sure it has some solid Resampling/Dithering options! Also, I was taught long ago to RESAMPLE[to 44.1kHz], and THEN DITHER[to 16-Bit]! In that order!
Try a few different plugins like I have done and see which ones you prefer!
Also, like Brian said, I ALWAYS do my settings at their MAXIMUM, since I want the highest quality every time, since it'll only be done once in my recordings history/life!