Gallien Krueger Backline 115 combo
 

Just bought a second-hand amp and i'm happy so far, it's just that I anticipate a need for more volume. So, reading the specs I see that the current setup is running into 8ohms for 115w. If the speaker is replaced with 4ohms impedance it will yield 175w. Can anyone suggest a 15inch speaker that would do the job nicely AND improve sound, yet be inexpensive. Thanks

Don't even waste your time

The difference in output between 115w and 175w is almost undetectable.

A second matching cab will get you noticeably louder,

Yes. Forget trying to "get all the watts", as that won't help at all. Adding a 2nd 8 ohm 1x15 WILL.

nice one. thought so. Thanks.