Why not RCU and OS? Why rule out Thunder Tiger Pro?

http://www.rcuniverse.com/market/item.cfm?itemId=606181

This is new, I haven't heard complaints about these at all, and it's nearly half the price of an OS with no measurable loss, in my experience.
Tower quality has issues in their engines, read the comments here.

http://www.rcuniverse.com/product_gu...m?engine_id=42

This is the best tool I use before buying anything I'm not already familiar with! What you could do is buy the Tower muffler for $14 (GMS is the same as well) and throw it on the Thunder Tiger or the OS and see a gain in performance over the restrictive stock muffler.