Well, this took me a while but I can finally report back on my experience!
I bought a dual output ATI X1300 a while ago that came with a twin VGA cable. This caused me a fair bit of grief as it took me an age to get the drivers to install correctly. Then, after about an hour of work, it didn't want to show many of the modes I fed it. I'm assuming that this particular card had issues with low dotclocks? Either way, very frustrating.
A while after that the VGA splitter I ordered from China arrived. This cost me a couple bucks and it looked nice enough... but I couldn't even get a single display to work with this cable let alone 2.
Tonight, as I was getting ready to wind down I remembered I hadn't checked the letter box. I went down the drive a found a package waiting for me! Ripped it open and it was a dual output X300 that I bought on eBay recently. A low profile model so I had to take the bracket off to stick it in my desktop.
Fired it up, re-installed the 9.3 drivers. Then, I lugged another TV into my room and hooked everything. Opened up CCC and chose "Clone desktop 1". Turned both screens on... BINGO! It worked!
I have to say, this looks really cool in action! Something about seeing multiple screens with simultaneous moving images... mesmerizing.
This has got to be the ultimate way to compare monitors: it's so easy to spot the differences in quality when they're running side-by-side. If I got the screens level on the same workbench it would be even easier. Already I could sense that testing screens one at a time (for image quality) has been tricking me: the individual differences between the Blaupunkt and Loewe I had setup where obvious when seen side by side yet the overall quality of each was less pronounced than I had expected.
So, it's confirmed: CRT_EmuDriver and GroovyMAME can be used with a dual output video card with two CRTs attached.