Allan Kozin spends an unusual amount of ink moaning about balances and the difficulty of playing the French horn in a review of a concert by Chamber Music at the Y.
What the performers needed was period instruments. The modern horn has a bigger sound than the 19th century horn. Check out, if you can find the set, John Eliot Gardiner's Schumann symphonies and the Konzertstuck for four horns, performed by the Orchestre Révolutionnaire et Romantique. Look up the demonstration podcasts at the Web site of the New Queen's Hall Orchestra, which plays using the instruments that would have been used by a British orchestra around a century ago.
Sometimes period instruments are the right choice!