your going to get a different answer from everyone here. any good quality base will work fine. stay away from the econo enamel type garbage bases. the sip universal clear is the big seller. i recommend the very slow activator for an overall.
There's lots of good ones out there, ProSpray, PPG Global,Nexa,DBC, Sikkens, RM, DeBeers, Any of the premium lines you can bet will hold up well.
Universal and MS Clear work really well.
DBU, I made a mistake-meant to type DBC. DBU is still available in some areas though, never liked the reactive reducer thing but I've been told by some of the PPG trainers that DBU was one of the most durable BC/CC systems they ever had.