You should check the spec on both player's output. Most are 2~2.5 V RMS through RCA and > 3.5 V RMS through XLR. Some do only 2~2.5 V RMS even through XLR.
Maybe the Rotel had significantly more VRMS than the Grant Fidelity? Were you using XLR or RCA through the Rotel? That also matters.