There is no problem that I see with conversion. The CD's themselves play too loud and so do the FLACS that I rip. I think the mastering is just too loud for my system but Wavegain improves the volume.
Interestingly, I have a bedside radio with a weak amp and the loud FLACS sound fine there. The problem comes with my big system (Jolida tube dac and Conrad-Johnson 250 watt amp), where the volume knob has to be at a very low setting.