There are coaxials that utilise external passive crossovers, not all coaxials sound bad actually.

If you are looking for a cheap and rather performing coaxial, i would say if you can still find the CDT Cambria, it'll be a good choice, or the Alpine Type-S coaxials, but if you really have the budget, it's best you get a component set instead as you can play around with the tweeter placement to get a better staging.