The Tekin is reasonably easy to program, but you do need a PC and a hotwire unit, as well as an extra cable (TT3848 HotWire 3.0 Adapter Cable). I have a couple of the Tekin servos and they are great.

If you have a mid-to high end radio, you may wish to get the same brand servo if you want to take advantage of the highest response speed mode of the radios. The Sanwa servos can also be programmed using their mid-high end radios. Usually the servos compatible with these modes are among the most expensive out there.

The high end servos from Futaba, Sanwa, Tekin, MKS, Protek and many others will all do great. Look for touring onroad specific servos, or their servos with a very fast transit speed (usually at the expense of lower torque ratings). Usually the more expensive servos have faster speed and better torque. They are often programmable. The Tekin servos can rotate freely and be centred from the programmer rather than just with the radio. The other thing that made the Tekin servos stand out to me is their use of a magnetic encoder rather than a potentiometer for sensing position, which they claim is more accurate and longer lasting.

Make sure you can get replacement gears for any servo that you do choose, these can be harder to find for older models. For your onroad cars it might be worth getting the same model servo for all your cars so that they'll all steer similarly.