Just my 2 cents worth, but I've owned a couple different generations of Proacs, and feel that the late 90s generation (Response 1S, 1SC, 2, 2S, 2.5, 3.8...) have the "soul" and emotional engaging quality that the later D-series is missing. I've owned the D28s and have gone back to the Response 2.5 with no regrets. Might it be the Scanspeak drivers that were later replaced with Volt?
As far as you're issue is concerned, think the idea of the 1SC paired with a good sub would work very well.