I think it’s a bad idea.
1st, both of those brands aren’t exactly highly regarded. Plenty of brand-bashing for both of them.
2nd, the Emo speakers are probably not any better sounding than your DefTech. A lateral move.
I bet most people would say that if you’re “changing”, then might as well sell the DefTech and start over with a brand that is more highly regarded like Revel, KEF, RBH, PSB, Focal, Dynaudio, etc.
If you want to keep the DefTech for surrounds, then at least get one of the top brands as your MAIN speakers. At least you can say that they are your main MUSIC 2CH system and the other speakers are just for movies.
Or just stick with what you have and save your money.