warmer pre-amp for Adcom GFA 555II

Definitive Technology BP20s bi-amp with Adcom GFA 555IIs and a GFP 555II pre-amp. SignalCable Analog2 ICs and double run single wire speaker cables. Too bright for my taste at higher volume levels. Considering replacing the pre-amp and looking for recommendations, something I can buy used for 500 or so. The Adcoms require 1.75v.
Audio Research LS3?

thanks