I'd probably go ET65 ... it's not really less efficient ... but it does sort of sound that way due to it's extremely organic nature. On the other hand, the Invader will sound a LOT like an opened up Green Back ... with a little more aggressive, urgent midrange ... also not a bad choice.
one of the concerns is the volume. It does have PPIMV but I have to run it extremely low if I use an efficient speaker.
Right now I am using the cab part of my Budda Superdrive 18 combo which has a budda Phat12 stock speaker in it which is about 103 db..... so if I can put a speaker with 98 db rating or so, it would be like doing 2 licks on an attenuator. Would Invader 50 handle the power? I mean I won't be running the amp full blast at any situation. The loudest I would go will be probably halfway up on the post phase inverter master like I said.
And yes I will definitely make a clip or something.
Are your speakers rated with caution? Like 50W amp cranked will put out more than 50W.. are your speakers designed with that factored into it? That would be great! I could have a peace of mind that I will never blow the speaker!