I have an old Model Power C628 or some such, (sorry I've had a few vodkas) anyway, I did a lot of work on it 20 years ago and it has sentimental value, so I installed a DH121 in it many years ago. I choose the decoder based on cheap, and other than Soundtrax, all non sound decoders are the no frills type. However, in a loco such as this, if you intend to run consisted with others, consider getting a slightly more expensive decoder which allows speed tables. Like you mentioned , the loco runs faster at a given viltage than other locos. A decoder which allows speed tables will allow you to run the loco with other, more "suitable" locos. Yes, you can alter starting voltage even with the DH121, but in the case of this loco that's not sufficient. If you're not concerned with consisting then any decoder will do. To answer your question, if the loco means something to you (or your son) yes it's worth it. BTW, I paid 3.99 each for 4 of those Model Power locos, back in the late 70's when no other Century units were available. Now Stewart has really nice units for about $100, but I don't need them! I'm about to buy a better decoder for it so I can run it in consist with a brass Alco unit I bought, which, BTW, doesn't run nearly as well! I need to play with speed table to do so. The DH121 will wind up in Stewart F units, which will run quite nicely with it, thank you.