Wort Cooling in Hot Weather

I brewed a batch on Saturday while it hovered around 90°. Let's just say my
trusty old 25' immersion chiller didn't get the job done. Hose water was
coming out close to 70°. It ended up taking 45 min to chill down to 75°
and
that was after I put my boil pot in a bath of water and ice packs. Simply
not acceptable. 

Trying to decide if I should add a pre-chiller to my existing IC, or go
with
a counterflow. I've never been hip to the counterflow idea, as it's more
difficult to sanitize, plus with 70° tap water I doubt it's going to
perform
much better.

What kind of chilling times should I expect from a 25' counterflow under
similar conditions?