John is right, you get what you pay for. A lot of what makes the ASP and Magnum so much cheaper is the lack of warranty and customer support. If you know engines or have some help from someone who does, they can be fine. But they'll never make the power that a TT or OS does.
As a beginner, I will disagree with the suggestion to go smaller on your engine. Those of us who have been flying for a while are able to do the nice long takeoff roll and manage our momentum in the air so that an underpowered plane flies well, but beginners need to have that power up front to pull out of stalls and do fast takeoffs at times when the wind is not cooperative or you just haven't gotten the hang of ground handling.