Here is an older thread I found that has the Monaco lineup and answers some of the questions on quality.
Here is one that shows what models between Monaco and HR are comparable.
Monaco declare bankruptcy in 2009 and eventually was taken over by Navistar. They continued to build coaches using up inventory but Quality started to suffer and they started putting the Maxforce engines in.
Also, at some point Monaco started to incorporate some of the pollution controls in like the Diesel Particulate Filters or EGR controls. Some of the effort was trial and error and there are some coaches the that aren't dependable. If possible try and fine a coach without these controls, probably a 2006/7. There are some slightly older that may not have the controls but you'd just have to check the specific coach.