The 1942 is the same size as most 1084s. It's a Bi-Sync monitor, meaning it can do frequencies around 15KHz and frequencies around 31KHz. It has trouble with stuff in between, so Super72 (24KHz) is out.
I'd definitely snatch the 1538 for that price - true multisyncs like that are the best monitor to have for non-graphics card Amigas. You can use any native screenmode, and it's definitely good to have a spare. Monitors like that certainly aren't getting any more common or cheaper. I asked Microvitec for a quote on their current 15KHz-capable multisync, and it's well over the $1000 range for a single unit (intended for industrial bulk purchases).
On another note, changing your Workbench Overscan prefs might help eliminate your Horizontal and Vertical centering adjustments.