question:Yorkville 520p connected to a 750p active speaker

[bosshoss]

my gear is:

 

triple rectifier w an orange 4x12

5150II w an old mesa boogie 4x12 bottom

GK 800 w an ampeg 8x10

keyboard w standard marshall 50W head and 4x12 bottom

vocals through a 520P(close, but not enough)

 

I tried a 550P with the 520P and it's still not enough. Can I buy a 750P and connect it with the 550P or is that going to cause problems? I have a standard really old conference style mixer, with one out, that's why I need to loop the 2 speakers together until I can pick up a real mixer.

 

Is this possible at all to do this? I'm bringing back the 550P today.

 

thanks if anyone can help me out with this.