I have a friend who recently bought an Ampeg BA115 to use with with his double bass. He has mentioned to me that he isn't completely happy with the overall tone, saying that the BA 115 has more than sufficient low presence, but that he can't get the string snap and vibration sound to his liking. If he decides to return it, what approx. $500 or less amp would you recommend? Acoustic tone is more important than volume.