Way too much power.

Either buy an LT-40 or a suitably sized engine for that LT-25. Assuming you're a beginner, being guided by SIG's recomendation will afford you the optimum training result. Learn to fly properly in the first place so you don't end up like so many here who never really advance beyond 'learning' anything much other than how to crash consistantly.

The most common mistake most students make is overpowering their model at the ill-informed if well meaning advice of self-proclaimed 'experts', mistaking forcefully delivered enthusiastic opinion for expertise. For a myriad of reasons I won't expand upon here which just a little genuine research and reading will reveal, the ideal trainer is best powered by an inexpensive simple air bleed carburettored plain bearing engine. Thunder Tiger, Enya and OS are just three manufacturers of many who offer proven reliable engines ideal for the task. Provided you also have a competent instructor, the money spent on such an engine and trainer combo is truly an investment which will save you a bundle in the long run in terms of the emotional and financial pain of crashing, crashing & more crashing as well as avoiding, until you're better informed, falling into the trap of buyer excitement driven wrong engine choices.

Buy what you need now, not what you desire, think you will in the future or others want.

I train studs with an LT-40 powered by an OS 40FP. You might find an equal, but you won't find a better training combo. Though properly engined, the LT-25 rates as a pretty good alternative. With sound reason, similarly IRL studs train & learn on a C152 or Piper Tomahawk, not a C-210 or Malibu.

My powerplant recommendation for the LT-25 in the training role would be to power it with a TT GP25. Cheap as, robust, simple and adequate. Once your skillset (not to be confused with confidence) grows beyond that, although you could up-engine the LT-25 with a ballraced 25 or even a 32 which will fulfill any desire for more power when you can hande the extra speed, but more so you'll more want manoeuvering capability. You will benefit yourself best by advancing onto another model type better suited to role.