I don't know if 25' is really necessary. I made a 10" jacketed heat exchanger, 1/2" interior and 1" exterior, just a straight shot. Recirculated it into the kettle and it reduced my cooling times by half using ice water.
Still too long but, I think 10 feet may be plenty.
What I would like to try is to make a tight spiral of 1/2" tubing and fit it into a 2" straight jacket about a foot long. Should be ample surface are for the wort to make contact, and should cause enough turbulence in both mediums to ensure even contact.
In fact I tried to make a coil tonight. it didn't turn out so well... Will probably end up farming it out.