In my opinion, the Magnum XLS (or ASP) has the best specs / price ratio. Mine turn around 18k on an 8x3 MAS prop. It out flew my OS .15 CVA, which a lot of folks consider the "gold standard" for .15s. I've had a couple of Norvel .15s but they never performed as well as the smaller Norvel engines, and the muffler connections were designed by Lucifer... Enyas are also good, but mine aren't as strong as the Magnum and cost nearly twice as much. Here's an ASP for $45: [link=http://www.hobbypartz.com/72p-s15a.html]ASP .15[/link]

I've never tried a Fox or MVVS, but have read good things about them.

EG