im so happy you've discovered some new music you like!
i agree, i would not neccessarily say that the 2 voice inventions are required pre-requisites to the sinfonias (which i agree with you, i tend to love these a lot, though i like bach and dig the much more popular inventions and wtc, these sinfonias i feel really are special! ).
i say definately go with what you connect with the most. the good thing about these (also the bad thing!), is that even when you get into something really 'difficult' they are all very short! so in terms of total technical demands placed on you (even if the level of writting is very advanced at times), are relatively kept in check by the fact that for each one, there just isn't that much total music to navigate (which again i think is the drawback, i soooo want some of these pieces to go on and on and on....).
have you had a listen to no 15 in b minor? it is an impressive piece! but not nearly as difficult to learn as many of the others (it will take a while perhaps to get the tempo up with those fast arpegios, it does have a lot of energy, but the melodic lines and 3 voice writing is not as difficult to manage which will make the initial learning and reading much more manageable, think more of a back and fourth conversation , question, answer, etc. vs fugue like where all three with the subject and development of the theme at the same time).
this one holds a special place in my heart, it is the first bach work i seriously studied and performed (for a jury) with my previous piano professor (it was in fact the first work i ever studied with him).
i like this one the best of all th yt uploads (gould is up but i actually it's too quick), schiff does it nicely!
this will actually be my next sinfonia (an overdue revisit) when i work back around to working through them next year.
i always thought this was his 'shredder', sinfonia!
