You'll find with marines 95% of livestock is WC.
there a few clown sp. dotty backs and grammas, as well as cardinals which can be tank bred, but I have never heard of any other marine species being captive bred in the aquaria trade.
Chillers are recommended - I have had many reef tanks in the past, and the last system I had ran a 250wt halide over a 2' cube, hence I needed a chiller to maintain a constant temperature. if it gets to hot, coral zooxanthella will die and the corals will bleach out and die generally.
id most definitely suggest a chillier for local temperate water species.
For the effort of temperate fish (and whats available), id honestly just heat the tank and get a lot of tropical species in a fish only system if your focus is solely on fish.
marines are all trial and error different thtings work for different ppl.
good luck with it and enjoy the game of marines, its the next level of fish keeping and can be amazingly rewarding.