Jeffrey, I share your admiration for Mackerras in Mozart (and much else). In addition to the recordings you mention, there's a fine set of the last four symphonies on Linn; you can read a review at https://www.musicweb-international.com/classrev/2008/Apr08/Mozart_Mackerras_ckd308.htm

I agree with you about the benefits of sampling recordings on line. I've always found Presto Classical's site very helpful in this regard.