Using a plate chiller to pre-chill your tap water will certainly help cool faster. The recirculating is the real problem. That's why it's taking so much ice. You have to let the heat run off with the water.
I use a 25', 3/8" chiller that I chill 5.5 - 6 gallons to pitching temp (~65*) with in about 20 - 30 minutes depending on what time of year it is. I am in the process of stepping up to 10 gallon batches, and plan to use a pre-chiller to cool.
Yah that is really a facepalm type realization. Simple logic should have kicked in telling me recirculating was couterproductive. Although I will say I used only tap water the first time running the water off and that certainly wasn't good enough to get to where I needed.
If I picked up a 30-plate chiller do you think I'd have a problem getting enough flow from my tap (outside hose) to run through the plater chiller and through the immersion chiller? I'm just not familiar with how restrictive the plater chiller is.
Ultimately I'd rather do this than build the attachment to make it a whirlpool chiller, if for no other reason but to have less to clean and keep sanitation simpler as I'm a newbie taking on alot as it is with my setup.