You will like the Evolva if you get one! I have one and it is very neutral and carries good corner speed. The Delta is an excellent car, and should be considered too. It uses all the plastic parts from the Evolva but the metal parts are made in house.
The XR8 from Power Racing, is a great buy! It is a bit better equipped (out of the box) and saves a lot of money (more to put into engine or electronics).
I have sold several Sirio .12 evo2 engines and all were easy to tune, idle well, and make great power. I put a pro .21 in my 1/8 and had a few problems... first a piece of the carb came off (inside) and destroyed the engine! After they rebuilt it, the rear bearing came apart and killed it again! The 2nd time I was just finishing break-in. The engine did run well. My problems were probably not indicitive of what one should expect from this engine.