and the nozzle check looks excellent- almost perfect.
mmmm... an "almost" perfect nozzle check. You must be a glass half full kind of guy, because to me a nozzle check is more of a glass is empty or it's full kind of thing- either it's perfect or there is a problem.
As far as your questions, I'm very much not a believer in 3rd party inks in Epson printers, the two exception being those who convert them to strictly b&w and those who convert them for dye sublimation processes. But it's kinda hard to really offer any suggestions, because I'm not sure what type of work you are printing on what kind of material ... what your short term and long term expectations are for your output.
As the previous poster mentioned though, 2 really isn't' an option. So either stick with the same inks, or flush and switch - and by this I mean flush the entire machine at the same time. otherwise your color will be drifting all over the place as you change each color, and one brand of ink may not blend appropriately with another and the color may even be a complete disaster.