Is it just me or does the Eshopps PF800 Suck?

good fix. this has worked well for me on the same loud toilet noise from other overflows. you can try an all plastic check valve on your return line instead of the siphon break, but they're not 100% reliable. you could make the siphon break hole low enough that it's in the water at regular operation, as long as your sump has room to take in the volume that back-siphons before the hole becomes exposed.

is that another tank in the next room?

 

on my 60 I use an overflow box and turn 750gph, on DT has 3 PH's that turn 1500gph
Just make sure your sump pump is matched to your overflow box......I like the Eshopps boxes....you will always need to play with the flow to kep the noise down on any overflow box.
I have a 2.5ft length of airline tubing stuck in the downflow pipe out of the box and wrapped back under the overhang part of the box
I also do not have the drain tubing attached to the top of the sump fitting..I have mine stuck straight into the sock itself....I hardley hear mine now Oh one more thing....I have a papertowel folded several times to fit over the top of the overflow box
I actually hear more from the return to the tank.... I have my flex output at near the top to give the surfact water aggitation...helps with gase exchange too.

 

Yes.