Hi again Goodonya
The setting of 24 max is very high, and can only be achieved by an ASV machine. You have basically two choices - Philips Respironics (which has been a big failure for you) or Resmed s9 VPAP Adapt. I am a relative newbie but I've spent a fair bit of time reading the forums, and I don't recall seeing anybody having the overheating and other problems you describe with the Philips. You may just have been really unlucky. The Philips has a lot more adjustable parameters than the Resmed, so it's easier to screw something up if you don't know (in detail) what you're doing.
I used the Philips for about a month before changing to the Resmed (which is what I bought). I found the Resmed much gentler. I recognise your description of the mask pulsing on your face, and the Philips did that to me. The Resmed doesn't pulse like that - in fact sometimes I wake up at night and wonder if it's turned on. For me, the Resmed was the better choice. It's slightly cheaper than the Philips here in Australia, but I believe it's more expensive in the States (I presume you're in the US?). By the way I just looked up one of the on-line sellers and the price is not as much as your insurance paid.
As discussed above, if your central apneas are endemic, then you will need an ASV machine to treat them. Did your original sleep study show the centrals, or was this something that developed after you started PAP therapy? A lot of people develop centrals under therapy, and it's a matter of reducing the pressure then gradually increasing it over a period of time. An APAP machine might do the trick. But I don't think there's any guarantee on that. Because this is being paid out of pocket, you don't want to lay down a lot of money only to find that the machine isn't treating you properly. On the other hand you definitely don't want to get a far more expensive machine if you don't have to. That's why I suggested renting an APAP and see how it goes.
Whichever way you decide to go, it would be a good idea to download and install some software so that you can monitor your own progress each day. SleepyHead is a user-friendly freeware program written by an Australian guy, and supported by donations. It has a few bugs, but most people find it more than adequate and easy to use. ResScan is the "official" program from Resmed. I find it more technical and less friendly than SleepyHead. You can find a link to download either program here: http://www.apneaboard.com/forums/Forum-P...-and-Links
It's probably a good idea to have a new sleep study but four large is a heckuva lot of money. I'm sure I've seen much lower prices mentioned in the forums - maybe you can shop around? Alternatively, you could try an in-home study. The DME will send you the kit, you wire yourself up and sleep in your own bed, then send the kit back and they extract the data. This probably isn't as thorough as a sleep lab test but is a lot less expensive. Having the test will give you a new baseline to measure your progress.
If I was in your position, I'd take the sleep test (assuming finances allow), hire an APAP machine and initially set the pressures wide open (usually 4 to 20 cm H2O). Download SleepyHead or ResScan and monitor your progress with them. Don't change the settings frequently - you need a couple of weeks to start seeing a trend. After a couple of weeks, you can adjust the pressure to home in on the correct setting for you (then leave it unchanged for a while to see if a new trend develops). If you're still getting a lot of centrals after this process you might have to consider the ASV machine after all.
Which ever way you go, keep checking in here. We're not doctors or health professionals (with a few notable exceptions) but we can at least provide the benefit of our experience to help you along.