Unless you'd have a dedicated room for your server, I'd advise you to go for workstation machines. Pretty much the same horse power with more affordable hardware without big noise issues. Also, in comparison to v4, Xeons E5 v3 are ridiculously low priced right now (e.g. ebay) and are one heck of the CPUs too. In general there're no substantial differences between the microarchitectures of the two (Haswell vs. Broadwell).
2U and especially 1U servers are much, much louder than normal computers. Shrinking parts means that the fans need to spin much faster to get sufficient airflow.
