ex91,
There are many different winch bumpers to choose from. Smittybuilt, TJM, Reunel, Warn, James Duff, and many more. A custom winch bumper would also be nice if you can find a fabricator, either locally or through mail order. Some of the companies that make custom Jeep bumpers could possibly help you. Check the magazines, especially the Jeep ones, like JP or 4 Wheel Drive and Sport Utility.
As for winches, I'd go with at least an 8000 lb. model, preferably a 9000 lb. one. The Explorer is really too heavy for a 4500 lb. winch to do the job. There's a good chance you'd fry it the first time you used it, or, at best, it would just overheat and stall. The naked truth is, good winches are expensive -- most of the time you get what you pay for. If it was me, I'd stay with a Warn or Ramsey. It's great to have a winch that didn't cost you an arm and a leg, but if it's not sturdy and dependable when you really need it most, then it's not much worth having, is it?
You can get some good prices on the older 9000 lb. models from Ramsey since they just updated their Platinum 9000 again, to keep up with Warn.
Keep asking questions.
DOGMAN