The reason why I'm interested in digital counter IC's is that I really need a lot of processing power.
It's very common for newbies to have very little feel for, what can be accomplished in a given time frame (and they rarely calculate it either).
That said, if you really want the counting to take place outside your microcontroller, just implement the counter of your dreams in another microcontroller - then you can make it communicate with the main controller in whatever way you wish.
One possible problem with an external counter (or divider) is, that if you want tight control, you need to read it very frequently anyway, so the time saving may be minimal and your resolution will suffer and could be just as good with a lower resolution encoder.
[...] by employing some clever algorithm.
How can you determine that you won't have enough time, when you don't know what the program are going to be?
Optical encoder is a bit of a pain to be honest,
Optical encoders are the
staple food in rotary encoding in robots.
things look much cooler with hall-effect encoder as you can make use of a tiny bit of the shaft sticking out from the other side of the motor.
If you wanna use a linear hall to get sine/cosine output, you will need to handle it through A/D-C inputs and that's very processor intensive compared to simple digital ticks.
A rotary Hall decoder, on the other hand is expensive and needs very
An optical solution is cheap and easy and if aestethics is your main goal, you're going to have a shell around the entire robot anyway, so nobody will see it.