Aspire is the best choice... Fitness First (4th floor of City center) does have everything you need to keep fit, only the pool is missing...!!
Al Thuraya near the Al Arabi sports club. It has aqua aerobics, gym and a spa.
Based on previous posts/threads in QL I would say your best choice is the Aspire Sport Complex, aside from Villagio Mall on Al Waab Street.
I think in City centre, close to Ansar Gallery, 4th floor.