Another option if you are not married to the combo dishes is to use the Neutrik Speakon to 1/4 adapter if you need both. Then all connectors on the dish are sealed.

The amp is inside the box? How do you get power?

XLR connectors are only supposed to be used for low-level signals, not high-current speakers, though Bose did try to use them as optional on some of their PA speakers. XLRs are for low-impedance balanced inputs or line-level. And you can't connect heavy-guage high-current wire to XLR plugs either. They're just not appropriate for the job.

Who said anything about the amp being inside the box???

That's actually a good option, I just wish the plates hadn't come pre-drilled for the 1/4" jacks.

The more I think about it the more I like it.

Maybe this?: Switchcraft : 1/4" Jack Cover

Or try just gobbing pure silicone on the back of the 1/4" jacks since its non conductive when its dry. I've done that before.

Back in olden times when XLR connectors were Cannon connectors, they had a rather high current rating. Like maybe 15 Amps.

If the amp is not inside the box, why do you need to bring line level into it?

Or are you planning on using line level connectors for power?

So I looked it up. Back in 1978, 3 pin ITT-Cannon XLR connectors were rated at 15 Amps per contact and #14 wire. 4 pin connectors at 10 Amps. 5 pin connectors at 7.5 Amps.