It's only $49n with a trade in. $69 without. Another option is the Tiger Shark .52 from http://www.kangkeusa.com/Engines/specs.htm
for $79.77--a little more power, at the same weight.
I've got one, and the service is as good as Hobby People's for their Magnum Products. Ebay usually has them, brand new, for much less.

Out of the bunch you have named, Magnum gets my vote. I have 6 magnums including the .46, all are great running engines. BTW, if you see a good deal on an ASP .46, or SC .46--they are the same as the Magnums, but with a dif case. Now that I think about it the ASP Super S52AII Engine was on sale at www.goldscallop.com for $79. That's what I'd do.
--Rick