That's OK. Once you upgraded to a comp set, you wouldn't want to run any speakers in your dash anyways.
Well, first off, the XXX isn't a full comp set, only mids.
I wouldn't necessarily consider the RE comps to be "better" then everything else in it's price range. Everything listed to so far are great performers at their price point. It comes down to personal preference.
You can mount them in your stock location.
But, for best performance, you'd want to do some things such as mount them to a solid mounting surface (if the stock speakers mount to plastic, it wouldn't be a bad idea to replace that with some MDF), sound deaden and seal your door, etc.