Youtubemp3pro.com is (fortunately) yet another Youtube to MP3 converter that’s completely online. Apart from a slew of ads, the site is very simple to use and fast, too.
The conversion process works by pasting the Youtube URL into the window and selecting the MP3 quality one would like the audio stream converted to. Unfortunately, there is no mention if the audio stream can be obtained as-is (that is, without quality loss through the re-encoding).
If you are looking to maximize the quality of your Youtube MP3s, I would start by downloading the video at several recommended Youtube to MP3 converters and taking the largest file (even though that’s not the best indicator).