Pre-amp for Harman Kardon AVI 200

I am new to Audiogon and not an Audiophile. At present i am using Harman Kardon AVI 200 with Bose 901 VI series speakers with reasonably good stereo sound. would an addition of good pre-amp make substantial difference to the sound, can you suggest a few models which goes with this combination. My budget is around 1000-1500 and I can go for a used one. Thanks.