Cool, uh, I mean warm! I read through this entire post waiting to see what the outcome was. A simple replacement of a thermostat.
However, the outside temps have warmed a bit, so are you sure the cabin temps are warmer due to the thermostat replacement?
As to the e-fan mod, I did that with my 2000 3.0 Ranger. I have the extreem opposite of you apparently; in Florida, we are into our usual "Africa hot" summers, so my A/C was not cooling as it should. A quick A/C check at the local garage showed it low on freon (long story; ended up replacing the A/C compressor, dryer (twice), and the evaporator for leaks). During this repair, the fan clutch was also replaced; at 213K miles, I'll guess it was overdue! When the new one was installed, the "roar" drove me nuts!
Since all the new trucks and cars now use e-fans, I went with the Mark VIII/Taurus fan setup. The key to this e-fan is the controller; buy a good one! There are cheap controllers out there, and this is when most folks who do an e-fan conversion get bit, then report back that an e-fan conversion is not worth it. If you buy a good controller (one with a 30 to 40 amp relay for the second speed), you'll be happy, and the used fan will run for years. I currently have a Mark VIII 2 speed fan (Taurus is simular) that I had for 2 years in a 2005 Ford F-150, and now that same used fan is in my Ranger. You can buy and easily replace the 2 speed electric moter for about 60 to 75 bucks if/when the motor burns out from your auto store or Jegs/Summit, as these e-fan 2 speed fans are very popular.
One other key factor is a temperature probe; stay away from the temp probes that are inserted into the radiator fins; these can seperate the blades from the tubes, making a small portion of the radiator a "dead" spot. get a probe that attaches under an intake manifold bolt. these are best. The better e-fan controllers come with these.