Is it sufficient to cool 4 TEC1-12708 (Peltier)?
Do you need small size or closed loop? If not, there are far better cheaper ways to provide cold water to your tec hot sides for cooling than a water block with fans.

A bong cooler can chill water to below room temperature, so gets you off to a good start with getting those hot sides cold. It's quite cheap to build one as well, one fan, and a pipe or container that can probably be scavanged or repurposed.