You don't have to use K-pro if you stick to a 50-75 shot. I've used it both ways, with and without k-pro / wet and dry. If you do the wet shot and stay below a 75 shot you will need the following:
Wet Nitrous Kit
Bottle Heater
Pressure Gauge
1-Step Colder Plugs
MSD Digital Window Switch
and that's about it. You can get a purge, but it's not necessary. Fuel pressure safety switch is an option.
If you want to run a bigger shot, you'll need k-pro so that you can control timing retard and a host of other tuning abilities. It's more efficient to run k-pro with bigger injectors and a dry kit, but it's also more expensive because of the k-pro and injectors.
So the main question is how big of a shot do you want to run, and do you want to do it the cheap way or the best way.