I've got a PDX V9 under the seat right now, don't really like it down on the floor like that. Thinking the glove box would be ideal, gives me a much shorter cable run from HU / to speakers as well. Bit of work to rip it all up just to test, hoping someone already has this setup going to confirm

 

I installed a JL 500x1 amp behind my glove box. U will need to remove a vent piece that vents toward ur floorboard. Then some zip ties to secure amp. Be careful to leave enough room between amp for the ac/heat mechanism to operate fully.

 

Yo, I always suggest to people to make a cardboard box the size of the amp you want to install and test fit it in a few places to see if it will fit. The PBR500 is slightly smaller than the PDX. If the glove box won't work, check under the steering column or in the stock location just behind the speaker pod in the front drivers side. I have put PDXs in both of those locations.

Here is a photo of my Arc Audio amp under the steering column. I think it is slightly longer but a bit more narrow than the PDX. You will have to ge creative with a mounting plate: