Asha's settings are very high quality, however the fact is that the stones themselves are much more pricey than common cz. This is due to the diamond coating which makes them more realistic, a bit more dirt resistant and adds diamond-like depth and crispness to the facets. Winfield's cz's are also fantastic. The great thing is that they also come in a range of diamond-equivalent colors, so you could get them in H or J color, making them even more realistic than the common D, IF of regular cz (asha's also come in lower than D colors).
As a favor for a friend, I snapped a bunch of pics and video of an Asha old euro cut cz next to old euro diamonds (the asha is loose and the diamonds are mounted in rings). Note the diamonds were lower color, however the asha performed very well.
http://s263.photobucket.com/albums/ii160/jewelsbyericagrace/Asha Comparison/
Nothing is quite the same as a diamond but the ashas and winfields are the closest I've seen.
Moissanite is a fantastic option too, but pricier than asha or winfields, though the durability can't be beat. MoissaniteCo is a great vendor who I know personally, and they distribute both asha and moiss. The problem with moiss is the greenish tint, particularly in overcast climates or low light conditions. But MoissaniteCo now sells treated moissy which is far whiter in color. I have not seen these in person.