Hi, my wife and I have a 2007 HR Navigator 45' w/tag, 525 Cummins, 4K Alison, 4 slides on the Roadmaster S chassis that has 10 airbags and shocks. It is pretty much loaded with all the bells and whistles, including three 15K AC units w/heat pumps (you can never have enough AC units in these bigger coaches and two just doesnt cut it), high-end appliances, aquahot, girard electric awnings all around, 12.5 KW Onan, etc. It has an empty weight of approximately 48K which is heavy. We do not tow anything. Prior to this we had a 2005 40' Gulfstream DP, no tag and a 400 Cummins, 3K Alison, 3 slides and prior to that a gas class A. A few of my observations and thoughts:
1. The Gulfstream was "fine" but we only owned it for 8 months before deciding to upgrade to a luxury DP with a tag primarily because we were not happy with the overall quality. It handled ok with no significant issues and the power was acceptable for our use. I must admit, even though the primary issue was the mediocre quality and lack of upgrades, I had also become obsessed with having a tag axle...why?....because I loved the look..dumb reason to spend the extra money for a coach.
2. The Navigator is on an entirely different level, in every possible way, than the GS but keep in mind we also paid significantly more for the Navigator and it also had an original price of $550K in 2007. There is some truth to the old saying, "you get what you pay for". We have had zero significant issues with the Navigator since owning it over the past 3+ years and we are extremely impressed with the quality of workmanship, materials, engineering, design, and chassis. The ride and power is awesome. No wandering due to wind or trucks passing us. A real pleasure to drive. I sometimes find myself significantly exceeding the speed limit on the highway because it is so smooth and significantly quieter than the GS. The downside to the big 525 Cummins and heavy coach is that the rig gets 6.4MPG average and that is mostly highway. It doesn't seem to matter if it's flat highway, hils, keeping off the pedal....that is what it gets. The GS with the 400 seemed to get significantly better but I never calculated the actual MPG but I have a definite sense of that. It was also significantly lighter.
3. I totally understand your dilemma regarding keeping a coach that you are very familiar with, have it sorted the way you want, like it, AND it's paid for. If you are fully satisfied with the Diplomat, I'd keep it and enjoy it....however, having said that...
4. If you are like me, once I start to look and "think" about changing and upgrading, then I become obsessed and it just has to happen, all there is to it, regardless of the reasons that I should keep what I have...it's a guy thing for some of us. The Navigator has a loan, it's insurance is higher, Colorado registration is higher, it seems like maintenance and monor repairs are higher due to the fact that the Navigator has a lot more complex systems and gadgets.
Conclusion: At the end of the day, we love everything about the Navigator. It probably was not the most fiscally prudent decision that I have ever made but we are happy and I consider it one of those "bucket list" items. I just wasn't going to be happy until I owned one of the best. Even my wife loves it and gave me the green light when I was researching and considering an upgrade. She told me that life is short, we've both worked hard all of our lives, put 3 kids through college, are financially secure, so go ahead...buy the damn thing. Plus after 35 years of marriage, she knows that if I didn't move forward, she'd have to hear my whining for the rest of her life. Sorry for the very long novel/posting but I do wish you the best of luck with your decision!!