mahler123,
The best listening position is the conductor's head on the podium. He is closest to all the instruments and gets maximum detail. He hears the best balance, so all the instruments are maximally revealed. All instruments are more or less directional in their radiation patterns, and they are all facing him with nearly full toe-in. (Incidentally, nearly all loudspeakers are directional, so to get the full frequency range, toe-in is desirable. The only question is whether you beam the speakers to each ear, or the nose.)
If the stage is high, like 4 feet in Carnegie Hall, then the first few rows will be below the axis of direct radiation from the instruments. At about rows 7-10, the radiation pattern will be more direct. Unfortunately, at 40 feet distance, the 10th row will lose a lot of HF especially, compared to the 10 feet distance in the 1st row. In my experience, the HF rolloff with the distant 10th row destroys the clarity and detail of HF overtones more than the benefit from the better projection. In the front balcony about 100-150 feet away, there is SEVERE HF rolloff, much multipath acoustic smearing of the midrange. The only benefit of front balcony seating is better visuals. Although there is more spatiality in the balcony, the large distance turns the whole presentation into almost mono. Ideal stereo separation might be the 10th row, but my paramount interest is to hear full freq harmonic detail. Front row center is best for that,
My most thrilling orchestral experiences have been when performing solo violin concertos standing on the front stage next to the conductor. All the brass instruments blasted into my ears and body. Subtle nuances from all instruments were unparalleled. The front row in the hall was the next best thing. Anything further back was boring DULLSVILLE by comparison.