I think you will find that one of the best performances of the Beethoven 5th ever is the Vienna Philharmonic, conducted by Carlos Kleiber on Deutsche Grammophon. It is sonically about average with most CDs, but the performance is overwhelming and a must own. It comes with a very fine Beethoven No. 7 as a bonus.
My favorite Dvorak No. 9 is George Solti, conducting the Chicago Symphony on the London/Decca label. A very commanding reading, and a good engineering job as well.