Small business accounting systems don't need super-servers, and Windows is on the client end with Linux on the server end, and throughput demand is absurdly low, even in a busy company. Also, vendors don't put out that much effort for my class of clients.
On the other hand, I can confirm that vendor tech support is quite competent - provided only their hardware and supported software is involved. If their stuff passes diagnostics, and still doesn't work - they're totally lost.
From the dim distant past, in simpler times, I remember the words of a formerly skeptical tech support guy at Digital Research when I submitted my ingredients list for a system that kept blowing the data. "That's all perfect, it can't possibly not work!"
In that case it turned out to be some unknown code fragment in the BIOS of the Everex host (Everex was a big name at the time) that kept blowing the data, but only with the exact setup I'd installed. Everex could suggest no fix. I replace the computer with an ALR (also a big name at the time) and all was well for 11 years. I don't remember for sure, but I think I sold the Everex to someone else and it worked fine until it died.
In a much more recent case, I had been building computers and maintaining the network for a fast growing firm. A guy named Jonathan rose to power and decided to go "all Microsoft" and "name brand" on the computers. He bought a hideously expensive Dell server - but same deal. Every once in a while it blew the data.
Something was wrong with the on-motherboard SCSI controller, but it always passed diagnostics, so nothing could be done. Finally it had a catastrophic failure, and the service contract had just lapsed.
So I ran home and in a few hours built a real cheap server out of junk and some stuff I was supposed to deliver to another company - and I bought a cheap Linksys NAS for off-line data. I never told him the NAS ran Linux or he would have had a seizure.
This cheap rig performed at least as well as the Dell and didn't eat the data. Jonathan disappeared from the face of the earth at about this time (not computer related) so management was free to have me build them a real server that worked.
But that's the bottom line. Start mixing stuff (and how are you going to build a working system any other way) and vendor tech support gets lost in the fog.
And the one thing I hate, hate, hate more than anything else is a server where everything is built onto the motherboard. You can't pull and replace until it stops failing. Even if you bypass an on-board component, and supposedly disable it, that doesn't mean it isn't still there causing trouble. These machines are too complex for anyone to comprehend, and too close to the edge of nervous breakdown for logic and diagnostics to prove anything.