There is another trick that we use here often. Several companies make a remote controlled A-B switcher for cable. MCM electronics sells them for $20 I think. We use this as a very basic inexpensive IR router, very often. There is one input, and two outputs, and both have discrete IR codes (A and B). You can simply intsall an IR repeating system, with IR emmiters on the components (your two pioneer DVD's). Then take the IR output from your block, and go to the input of this RF switcher. Best way to do this is to use a $1 F-RCA adaptor. Then get a short RCA cord, cut it, and use the 2 conductors for your IR in (signal and ground). Then do the same thing on the two outputs. Two adaptors, two cut RCA cords, hooked up to your IR emmitters going to the Pioneers. Now, if you hit "A" on the remote, your IR will only travel to DVD player on that output. Hit "B" and it goes to the other DVD player.

This is a very inexpensive IR router trick that has worked for us for many years.