Claud,
I would not expect a less than optimal match to sound bad. Some might even prefer the sound.
Generally a higher amp input impedance can help assure lower distortion and better dynamics, especially with tube pre-amps which tend towards higher output impedance by nature, some more than others. It can also vary by frequency in a manner taht is not reflected in published impedance specs. So its a matter of degree more so than good/bad perhaps. Also its more of an insurance policy to hedge your bet towards better results in that exact results cannot be known in advance or in lieu of an apples/apples a/b comparison.