just be sure to get DOT fittings if ya get those push to connect ones! dont buy the cheap ebay ones that are not DOT aproved! i still have a dam ringing in my right ear! it will probably never go away just because one of the fittings blew off! when my head was near it trying to find the leak.
IMO i would go with brand new valves just because MOST PEOPLE only swap out valves when they have problems with them... and only way to find out if they leak is to hook them up to something and wait overnight or so used ones can be a crap shoot.... thats why i have leaking valves just sitting in my toolbox.lol bought them used from some guy on southside.
with a full bag setup i would not risk the hassle! spend alittle more cash and go brand new! cause the first bad tiny leak you have with some used ones will piss you off so much you wish you just bought brand new after afew days if its just a small leak overnight!!!!!
sometimes i wish i got 1/2valves but 3/8valves just easier to fine tune. 1/2 just have alittle more fun! and you can get slowdowns for them BUT why pay more for valves only to pay more for extra items to slow them down. atleast thats how i saw it.