Hii Eddy
Yes you can go with rack server. It has so many amazing features like has good configuration which includes varying levels of adaptability and accessories which includes shelves, fans,vertical rails, power strips etc. so that you can customize the server rack as per your need. server rack security will provide you amazing security.In its most secure form, server racks are fully protected with four sided doors/panels and multiple locks.So you can easily go with it.
Well I guess that assembled racks are enough reliable in term of stability, I had been colocating an assembled rack for more than 2 years and it had not encountred any problems at all.
Good luck