Cymbals are loud and non melodic. Sizes and alloy quality also come into affect. Loudness and quietness also are affected by sticks (width, taper, tips), hand control, finger control, wrist control. I've played in many situations from classical orchestra to death metal in the last 12 years and I'ved used the same 22 in orchestral hand cymbal as my ride in all situations. I've bashed it, I've rolled it w/ mallets, swung the shit out of it, and funked it up. You want loud Rock cymbals, use 22in crashes Rude, HHX, AAX explosions, You want quiet use A's and K's ...use 14in and 16in fast crashes. But you also have to be able to control how you play them.
The drummer in me says ... If your guys think that the drums are to loud tell them to back the f*@k up. But trying out proper cymbals might help alleviate their trouble. In case it hasn't been said tell them to buy some ear plugs and shut the hell up