Normally I would say get the 40 size plane and use the engine from your trainer. Since you want to keep the engine in your trainer though, I say go for the Pulse with the .75-AX. The engine is very user friendly, powerful and reliable. You should have an easy time with it and keep it around for many years. The Saito 100 is nice too (I own one) but maybe not for a second plane. Just my opinion.

Keeping the trainer together probably isn't a bad idea. You never know when you may feel like flying it again.