how does this system setup look?

Yes, whether they are dual voice coil subs make a difference!

If the subs are single voice coil, you can only get 250watts RMS from the amp. You'll need the dual VC subs in order to get the full 500watts from it.

Again, what are the dimensions of your enclosure? ARE they dual VC?

You'll need to pull one out and see how many speaker connections it's got. If it's got 1 + and 1 -, it's a SVC. If it's got 2 +'s and 2 -'s, it's a dually.

Now, that I know the specs of your amp (500Watts RMS), it's a good thing you asked about the 300Watt RMS RF amp. You'd've been downgrading by A LOT!

Just b/c there's only one set of wires going to each chamber on the box doesn't mean they are SVC.

We need to know what you have. You'll need to remove one of the subs from the box. Seriously, stop worrying about getting more power until we know what you're working with. I'm tired of repeating myself

Not at all.

Find out if they are single or dual VC subs, and carefully note how they are wired. If they were installed 'professionally', then I'd assume they sold you the DVC subs  wired parallel/parallel to get full power from the amp.

If they are DVC, wired to 1ohm (ported box, BTW) then you're getting about as much out of your setup as you can get. Still, if it was a prefabricated ported box, then you can build (or have built) another one for more efficiency, but not much more.