I have to agree with psonic, for background music in a weightroom, unless it's the size of an olympic indoor track or something, the H/K should be more than fine.
I've seen many,many gyms use H/K, Yamaha, Denon, Kenwood, Sony, etc. receivers for this.
Now, if you're blaring music at PA system volumes like at a basketball or football game, you're gonna need more muscle.