Jett engines
Vasek,
The nice thing about Jett's is that they break in easily, run on 15% nitro and standard, inexpensive KB 1L plugs and run right out of the box.
Tell them what you want to run and they will tune the system for you, adjust the carb, even set the needle valve for you!
They are outstanding engines but yes, they are expensive. If you are willing to pay the price of admission for a no hassle, no fiddling around, run right out of the box powerhouse then by all means buy a Jett.
There are other options out there such as ducted fan and racing engines but I am not qualified to give advice there as I have no experience with them.
Luckily plenty of other forum members do!