(I think) I'm going with the Super Tigre .45.
I downloaded the manuals for the engines I can afford. The ST manuals have wonderful break-in directions, which are very easy to understand for a new flier. It comes with a 3 year warranty, and I even called tech support for a question and got fantastic customer service. The power difference between the .45 and .51 seems almost negligible, and the .46 will fit easier in .40 size planes. I like the idea of higher rpm's over the .51 for speedy flying. Last, the Super Tigre engines are a great deal, and are even designed to use 10% nitro fuel for break-in, with a synthetic blend of lubricant, while Magnum calls for a 20% Castor Oil lubricant for break-in.

My only hesitation comes from Missleman's difficulties with Super Tigre; other people with a good amount of flying experience seem to have no reservations with Super Tigre.

Thanks for all the input. Now hopefully Tower will get them in on schedule! They're actually out of stock on many engines in this size, which makes me think they've got to do something about that. If not, Magnum is a good (in stock) second choice.