ORIGINAL: smokinbarracuda
Well from what I've seen I'll list the different options available:
1 - Non smoke n sound (rx13)1 or 2 speed forwards and backwards. All plastic tracks and gearboxes
2 - Smoke n sound (rx14 or rx18) 10 speed forwards and backwards. All plastic tracks and gearboxes unless specified as metal.
As far as I'm aware none come with the 3:1 boxes installed but some places do install the normal metal boxes, tracks and sprockets for you but at a much higher cost. I also assume its the same for the infra red series as the airsoft.
Actually, the RX-13 was the first smoke and sound (SNS) control board HLmade. It was replaced in subsequent iterations by the 14 and the 18. But, you're right about the 2 basic options. The Raidentech tanks that have 2 speeds do not have SNS and either go or are stopped. The SNS tanks have the proportional control, which is really a 10-stepped speed controller instead of truely proportional speed. But, it is much better than 2 speeds and does a decent job of approximating a truly proportional controller.
Unless you're buying a custom tank, no one sells one with the 3:1 gearboxes installed. That has to be purchased and installed separately. Generally, you buy the SNS tank for the proportional speed if you're getting 3:1 gearboxes.