I don't think it was smart to throw all the stuff away. Most of the time it wont just stop working. I use some of my dads heaters and one filter that are 40 years old and they do better than new stuff!!
Either 25 Watt heater will work in your 5 gallon. I am not a fan of pre-set heaters. As, I have found there are instances that usually come up where heater adjustment-re-adjustment of temperatures are required (Winter, Summer, Parasites, Treatments, etc). Don't quote me on this: but, I am thinking that the Elite 25 Watt is adjustable and not a pre-set heater. Hopefully, someone will come along and verify that information for you.
If this is the 25 watt Elite you're looking at, it is adjustable. I agree that it is definitely worth it to get an adjustable heater; they are so much more consistent, and I love being able to control the temperature if need be. I wasted money on all kinds of preset heaters until I got Marineland and Elite adjustables for my small tanks; I'm so happy with the heaters I have now.
Hagen Elite heaters are excellent heaters. I know a few people that have them. I just don't know anyone personally that has one of their 25 Watt heaters. But, that information was just verified for you by LolaQuigs. Fluval products are excellent, as well. I am just not a fan of pre-set heaters. I have a Fluval 50 Watt heater in my 10 gallon. I also have a Fluval 100 Watt heater for my 10 gallon. To be placed into the 10 gallon during January and February when it gets extremely cold where I live. This is because the ambient temperature of my residence is several Degrees lower than tank requirements. For your 5 gallon tank, I wouldn't go more than 25 Watt for any reason.
I have the 2 of the Elite 25, it works great and I would totally recommend it! I also have a Topfin 25 as well and it is also really good, though I like the Elite better since the Topfin looks kind of large in my smaller tanks.