You call that a complicated setup? Four modules and a controller? I've been using a setup like that for twenty years now --- and at times it was complicated by many more than four modules.
If you have a non-laptop computer PCI would be the way to go, and it's not hard or dangerous to install a PCI card if you take the proper steps with the anti-static wrist strap and the usual stuff like unplugging the machine before you start to work on it.
Once you get the card installed (and it IS big enough for your purpose) it needs to be recognized by your operating system. Just drop the CD that came with the card into the drive and follow the instructions.
Plug the midi out of the P200 into in # one of the interface, then make two chains --- the first starting at midi out # one with the Motif's midi in, then chain the korg (or is it Roland?)
DR880 from the Motif's midi thru. Then repeat the process with the Triton and the Roland sound module, starting with midi out # 2 and using the midi thru of the Triton into the Roland module. Now you'll need to make sure no midi channels are duplicated - set the Motif for 1 thru 12 and the 880 13 thru 16, then set the Triton to receive on 1 - 8 and the 2020 on 9 thru 16.
Then, with the addition of some midi recording software you will be all set. Let me know when you're ready for my recommendations on that front...