Aha, well I didn't catch your $60 cost before. My quick ebay look was showing a few MultiSyncs at ~$300 ... one unit at over $3K! (Seemed a little shocking/stupid to me, given that these old monitors didn't cost that much when new. Then again, I've seen Apple II computers sell for $9K and D&D books sell for $700 and domain names sell for $200K ... collectors will pay premium prices for all sorts of random junk.)
$60 for a 29" monitor ... that's actually pretty good. I'd go for it.
Even if it's a bloody huge 2½x2½x3' cube which fills up the entire desk, and weighs 100lbs. Assuming it works and doesn't have any excessive burn-in, dimming, fading, or other wear-and-tear problems. Assuming it doesn't need any costly repairs or mods (like new fuses, caps, transformers, aftermarket cooling) to continue working well. Assuming the shipping costs aren't ridiculous.
The signal box does promise greater convenience and compatibility and portability, since I assume it's nowhere near as bulky as a 29" CRT. But it might create it's own problems, not actually be 100% compatible, make visual artifacts, force compromises, who knows? I'd expect that these things will be around for a long time (whilst 15KHz monitors become extinct), and they might even get better but I doubt they'll ever get cheaper. Again, do the monitor - you can always buy a signal converter later.
Of course you could hack/mod each of your retro devices for more modern output. Rip that analog crap right out of the loop, lol. Sort of like ppl upgrading their ancient 6502/Z80 machinery with cards that add 20GB CF storage or whatever. (Incidentally, there's now an Apple IIx VGA card, apparently.)
