Hi Kay,
Welcome to the forum.
Amplitude 2.5 is a program shipped with Band-in-a-Box. The program alters the sound of audio to simulate the way the audio sounds when played through a guitar or bass amplifier and speakers.
Band-in-a-Box is a 32 bit program so VSTs need to also be 32 bit or you will need a utility program that lets 64 bit VSTs work with 32 bit programs. PG Music sells the utility program jBridge. The Windows version is available
+++ HERE +++. There is also a jBridge for Mac but you will need to contact PG Music Sales for that as I can't find the page link.
Also, you might want to investigate free VST instruments. There are many, many great sounding piano VSTs available. Start at
+++ KVR Audio +++