From what I’ve seen/heard, Koss speakers are pretty cheap and don’t sound all that great. Even Pioneer’s had their day, but they’ve been cheaping out a lot too. Unless you get into the high-end stuff anyways.
If you’re going fairly low-budget (like maybe up to $150 CDN for the pair) just stay away from paper cones 
As for cutting the holes in your cargo cover… it works, but if you remove your cargo cover to squeeze somethin in your trunk, it’s a pain in the ass. My gf’s '91 Si has 6x9’s in the cargo cover and I curse that thing every time we put ANYTHING in it… Pretty easy to install though if you don’t need to take out your cargo cover very often and decide to do that…