
RE: Resmed S7 Autoset Spirit VS. S8 Vantage
Bwool, I have both machines. I like both a lot. However, I'll point out some advantages and disadvantages if I may.
Autoset S7 Spirit (older Resmed model machine)
1. Very quiet machine.
2. Great for sleeping with you and a bed partner who may be sensitive to noises.
3. It's an APAP machine actually. Pressure or the CPAP therapy can be set to a multitude of pressure H20 ranges 4 - 20 cm. It depends on you, but mine has averaged around 11 cm or so. Anything higher and I have difficulty being woken up (i.e. a hurricane of air!).
4. Kind of heavier for travel with humidifier (i.e. 5+ lbs.).

A gigantic pain with the TSA in U.S. airports as they demand you have it out of any travel bag for close inspection and swabbed for explosives residue.
Autoset Vantage S8 (latest or newer Resmed model)
1. Noisier machine (less insulation, thinner smaller cabinet)
2. Very effective though, works very responsively.
3. Lighter weight by a couple of lbs. at least. Smaller that S7.
4. Better for frequent traveling. Still a pain for any airport TSA inspections but slightly better in handling.
5. Same features as S7.
6. Really small IF you don't need humidifier (I do).
In conclusion, they're both very good machines. After some years with the S7 though, I didn't think it was working correctly. The variable pressure didn't seem variable like it once was. It starting blowing really harder pressure and I couldn't stand it. Felt like the full face mask was gonna blow off my face. I sent it in to an authorized repair station. They claimed they reset it to factory settings and NOTHING was wrong with it.
I hope that this helps you partly in making a better decision. Let me know if I can assist further.
Sleep well!
Harlan