Concerning the Blueline pump?
Eh well isnt one of the blueline pumps the 50z?
Except yellow? Remember someone asking "does anyone use these pumps?" and BillA saying "thousands use the ###" where ### was some blueline model that looked exactly like the mcp600/50z
Anyways... It depends on what blueline. anything that gives less head than the 50z wouldnt be advisable. Anything that pulls a lot more power isnt good. the HC you havent isnt very large so any pump that pulls a good deal more power is just going to raise your temps unless it ups your flow some unrealistic amount. Your setup is very simple and doesnt need a lot of pumping power as its not that restrictive. The idea pump for you is most likely the 50z.