I worked almost exclusively on Class A motor-homes in the late 90's and there were a few front engine diesels around. It seems to me they were a John Deere chassis and used a GM 6.2 or 6.5L turbo diesel and truck version of the Turbo 400 transmission. I thought the one or two that I actually drove were noisy to drive, but we only did a 2-3 mile test drive most of the time.
This summer We had a really nice late model front engine diesel next to us for a few days. It was a Freightliner chassis, and I talked to the owner a bit. He said they get over 10 mpg, and I think he said they averaged about 13mpg, and that is pulling a Ford Edge toad on a towbar. I asked him about engine noise and he said it was quieter than their previous F53 chassis coach.
It might be worth a look and test drive,definitely a test ride, don't want to find out as you drive it away it sounds like an M1 Abrams inside on the highway.
The most important opinion in this whole situation is that of your DW. You may love it, but if she hates it......wellllll.
Dave & Kandi & Indica the Chorkie pup "Big Blue"
2001 Holiday Rambler Admiral 30D w/ 2nd slide
2000 P32 7.4 4L80E wide track J71 18/21K