Maybe I missed this somewhere, but how big is your tank? Whatever filter you get, make sure it's rated for at least 3X the size of your tank. Going bigger is definitely better if you can afford it (upgrading is a pain and winds up costing more in the long run). I have the XP3 as well, and it does a good job.
For a heater, look for a fully submersible one with a thermostat you can control (not a pre-set one). Ebo-jager and Tronic are two reliable brands. And although Ebo-jager's heater has a water line and the company says not to fully submerse the heater, it's OK to do so.
You may also want to get a heater guard. All these things can be found at
www.bigalsoneline.com