I have the TH .46 which is pretty close to the GMS engine and muffler.

I also have O.S. .46 AX, O.S. .46 LA, and Evolution .46s (I do have other brands, but not in .46).

I would rank them in this order with the top being the least noisy.

OS .46 LA
OS .46 AX
Evolution .46
TH .46 (about the same as the GMS .47).

The TH .46 is definitely the loudest.

The TH .46 and the OS .46 AX produce about the same amount of power and both are pretty powerful little engines.

The Evolution .46 is no slouch either. But it is a tad louder than the AX.

Of you were trying to choose between the GMS and an O.S. the OS is just easier to deal with hands down.

The GMS is far cheaper but you'll spend far more time getting it broken in and tuned up than you would with the OS .46 AX.

The Evolution, well, I LIKE the Evolution a lot, except for those lousy limiter collars that you'll want to remove.

Once you remove them the needles tend to walk. A lot of unneeded grief. Something that I'm going through...

(Anyone know of a drop in replacement carb for an Evolution 1.00NX with the same "walking" problem?!).