Herbies are silent and no gurgling, Durso and others draw air so they will gurgle a bit. Depending on flow might not be that bad.
If tank isn't tempered could always drill a third hole but not the end of the world to go over the top for the return if do go the Herbie route. Can even do up a little
manifold.
Plumbing; HD/Rona has lots, plumbing supply shops carry that one fitting you need and HD/Rona doesn't. Hot-tub places have lots of stuff as well and don't forget the LFS though might by the most expensive of all but do have thinner walled bulkheads. Herbies work best with a gate valve and that might take some hunting to find locally.
There is truth in the measure twice cut once, dry fit, make alignment marks. Spaflex can help a lot and glues into standard PVC fittings. Use primer and glue and need to give the twist when putting together.