Long ago I tried Flac after using mp3's, but the improvement was not that noticeable. I then installed Sound Solution and it was a major improvement. I use #69 after testing all the selections and never switch as it is perfect for my taste. I run my audio out through a Pioneer receiver into some high quality bookshelf speakers. I also use the KX drivers for my Soundblaster Live 5.1. I am super happy with the sound. With this setup good quality mp3s sound about like the original cd.
But, since you asked what other #'s are good I would say #79 is quite good as are 84, 37,38,39,40,41, and 42. If I had to pick another it would be #79. After trying #79 again it might be as good as 69. 79 with somes songs is sweeeet.
After listening a bit more I would say that 79 gives more boost{volume} and also gives some reverb like on an outside soundstage. If you like a little reverb you will like 79. If I turn the volume up a notch while using 69 it sounds as rich as 79 and I find 69 generally a little better as it has a cleaner sound, but for some songs 79 does it for me. Bear in mind I have a different sound card and am using KX drivers. This may change how good you find some of my picks since your setup may produce somewhat different results. Sound Solution is a more sophisticated plugin than just changing eq settings.