Do you want your pins to play them or to look at them?

If you want to play them, just get your favorite pins with good PF condition and 100% working (or non-working and fix it up yourself). A professionally restored machine will not play much better than a well maintained and working one.

If you want to look at them and have them look absolutely perfect, well, drop as much cash as you feel like getting one that looks perfect.

Since you're keeping your pins in a line, presumably, so you only need 2 cabinets with one side in good enough condition to not bother you (less if there's a wall on one side of the line). The main difference with a professionally restored machine is cosmetic - most of them replace all the plastics, broken or not, redecal the cabinet so it looks perfect, etc. The question is whether it's worth thousands of dollars to have a perfect cabinet and perfect un-faded, un-yellowed plastics, etc. Someone recently posted pictures of the "terrible yellowed" plastics they were throwing out because they weren't perfect - none of them were broken, and you wouldn't know they were yellowed unless you took them out of the machine and put them next to new ones, but they were still pitching them. I think it's crazy to pay more for CQ machines, unless you've got more money than you know what to do with (in which case I could suggest some things which have nothing to do with pinball!).