Will these pumps fit into a redsea nano max sump?

[Sind3rella]

Hi there, new to the hobby. I’ve got a Red Sea max nano (all in one tank). 
 

I just purchased a chiller as I live in a country where it’s hot as heck all year round. At the LFS, the owner suggested an OASE pump which had the ideal flow for my chiller, however to my dismay, it did not fit in the sump (was too chunky).

 

I’ll keep this pump for the future when I inevitably upgrade my tank in a few years time. However I’d like to know if..

 

1) I can use the return pump for my chiller. I’m not sure if it’s powerful enough. My chiller requires over 1000-2500 litres per hour. 
 

2) a Sicce Syncra Silent pump will fit in the sump

 

3) any other suggestions

 

Any advice would be greatly appreciated. I don’t want to buy another pump that isn’t going to fit. Thanks!