I had a pioneer HU with one pre out which I had connected to my 4 channel amp then I wired my speakers and sub from there. It worked fine.
I just bought an new pioneer 4200 ub and it has 3 pre outs, one for front, rear and sub. I assume this means I run 3 sets of rca cables to my amp rather than just using one to deliver the signal.
You can still connect your new HU the same way it was using any pre outs but the one for the subs. I find the crossover on most HUs rather limited anyways, also once setup you don't really need to change the gain for the subs all the time.
So Joe are you saying I should use the pre out for the sub and one for my speakers or should I just use one pre out for all? What is the best way to connect?