Thank you for your thorough response on diaphragm-pump units. The air supply was the one big technical issue I could only guess at after reading the thread, which was otherwise quite clear to me.
I certainly don't mind doing a bit of fix-up. I've capriciously modified perfectly functional commercial products to my tastes since I was a teen (which was longer ago than seems possible; I'm going to have a long talk with my mirror about the clearly faulty "white balance" in my hair). In fact, I've often felt hobbled by warranties -- they are lovely to have, especially for items you rely on, but when the warranty ends, the freedom and fun truly begin. More often than not, it's faster, easier (and dare I say 'more reliable') to fix it myself than abandon it to the tender mercies of a distant authorized service center anyway.
I originally leaned toward a WEP 858D, simply because an out-of-town friend has one and likes it (alas, a personal inspection is impractical), but ironically, the strongest deterrent was that it happens to have the cheapest total price on eBay and fastest US delivery at present (from one seller; others charge more and ship slower) My second and third (and possibly more) choices were American 2-in-1 or 3-in-1 stations, some with diaphragm pumps. Hence my questions.
I knew that pro units seem to choose the pump, but my heart favored the simpler mechanics and wiring of a fan handpiece vs a more complex pump and silicone tube/cable hybrid -- especially should a repair or replacement be necessary.
I expect the US units to have better consistency, quality and local standards compliance (they have more to lose), yet at least two US models (one with a diaphragm) manage to be only slightly more expensive on eBay, all things considered, despite what I assume must be higher costs (can the edge lie in shipping?) I'd likely chose those, but their footprint is MUCH larger. (Maybe they get those cases/parts cheaper?)
I have a large workshop, but no matter where I sit, I can only reach X sq ft of bench/shelf -- a silly but real obstacle.
Oh well, the bank called this morning to report "suspicious activity" on the card I was going to use (though all the transactions I see are with US retailers I've bought from before), so I guess I'll wait until all that is sorted out on Monday.