Thanks for your in-depth reply dlanor. One part of OPL I never tried was USB games. I've only tried USB games using USBAdvanced. Probably explains why I ran into problems with a few games.
Regarding why I called Routers a hassle. I just meant that since my router is far away from my PS2, the only viable way to do a network connection is if I get a spare router out, which takes up space. So with a gigabit port on my PC, I could just connect my PS2 and PC directly. However now that I think about it a crossover cable would negate the need for a gigabit >_<
I was under the impression that with a decent rig one could run PS2 games on PCSX2 just fine, even if it is demanding? I want to ensure my next PC purchase can run PS2 games :p