My two cents:
It's best to go with two filters rather than one. Especially in tanks larger than 30g or so. Not only will you get more GPH, you will also expand your media options and your filter surface area. But most importantly, you have a backup in case one fails. Other benefits include the ability to maintenance them on a rotating schedule, ensuring that you never accidentally cause a minicycle. And your media will not require cleaning as often since the dirt is spread out between two filters instead of one. Say you had two tanks of the same size and equal bioload, and one had only one filter and the other had two, you would be cleaning the media in the tank with one filter twice as often. So oddly enough, it's cheaper to run the two when it comes to media replacement because you won't do it as often. It's kind of like wearing one pair of shoes every single day compared to wearing either of two or three pairs.
I usually go with a combination HOB and canister.
I hear Stealth heaters are good. Never had one of my own, but I probably never will because I've had nothing but great luck with Rena.
Why do you feel a need for two thermometers? A normal sized tank with a good heater and filtration shouldn't have any manner of drastic temperature differences which would necessitate such a thing.