I don't know about the cost of components or how important the cost might be to you. For small varmits the 204 would do very well. I think it would have the best barrel life. The 243 and 22-250 would offer a little more versitility and wind bucking properties.

Since this is stuff that you already know, all I can add is that only you know what you want from this rifle and your shooting and cleaning habits. I do know that cleaning these little speed demons is very important to barrel life. Its its just for varmits and targets, I would try the 204. After all thats the only way you will ever know for sure.

I have to admit that Z has a good point there as well.