Where possible, try to find a high quality aftermarket that often supplies other OEMs.
I would generally use Gates for timing / auxiliary belts.
Clutches seem to be a bit pot luck, as a lot appears to be rebranded / re-boxed. I purchased Sachs branded parts. When they arrived, LUK part numbers on the components themselves.
Not too sure on gaskets and alike.
To me it's more complicated to answer this question than it used to be.
