@amoskodare - How do you find your setup with the Sam440ep-flex? I was originally looking at that exact same spec setup. The price is about right and it appears to be the best OS4 bundle for the price.
@Rob - 3rd time round buying and selling, always get a pang of nostalgia and buy again. Loosing a lot of money doing that. Will hold on to the 1200 :-)
Not wanting to sway you too much, but as others have said, try before you buy. I speak objectively as an OS4 and MorphOS user, a Sam 440 is too slow for me to be comfortable with at 400-667mhz and with just one PCI slot (which you'll fill with a graphics card) there isn't really any expandability over say a Mac Mini (which is more than double, if not triple the speed). Heck, I even find my A1XE a bit too slow at 933mhz, watching the CPU meter spike up to 100% whenever I load a more than basic web page or open programs etc, even taking a screenshot sends it way up, I certainly feel the difference between my 1.5ghz mini and my A1XE. On the Sam 440 you're not going to have much joy with video files and DVD playback.
At the end of the day, it's really down to OS4 or MorphOS, personally I use both and like Som99 above me, I also spend a lot more time in MorphOS these days, I found development on the OS4 at OS level seemed to have slowed a lot in the last year where as MorphOS has jumped 4 major revisions, most of the recent major components like Odyssey, MUI 4, MPlayer etc. all have the latest versions on MorphOS and are backported to OS4 some time later, also a big part of my "NG" experience is using old Amiga apps too, I find the ones I use regularly seem to work better and have more compatibility in MorphOS. I also find it more stable and get less crashes, although that's more than likely down to the instability and flakyness of the A1XE board.
I will say OS4 does feel more like OS3 as it still uses Workbench, but if that's a major thing for you, you can always replace ambient with Workbench if you wanted, I personally like Ambient now I know my way around it though, Workbench feels bit basic in comparison.
No flame wars from me, you make up your own mind, but I used OS4 for years and since my A1XE got flakier over the years I was looking to replace it, for a decent OS4 experience I needed a SAm 460 or X1000, the cheapest option of which was still close to a grand. I used OS4 daily from 2007-2011 and would have loved an X1000 but the bank balance (and the missus) ruled that one out, since getting my Mini in 2011 I've grown to prefer the experience anyway.
You would certainly be happier with a Sam 440 than a classic PPC card, but don't write off MorphOS just because you don't like the look of a Powermac G4 (which will likely be hidden under your desk anyway, or put it in a new case?) or the Mac Mini G4, not sure what limitations put you off the mini but I can't say I notice any.
Another option would be a used Pegasos 2, you can run both on that machine, iirc there's one on Amibay at the moment for 600 euro.
Just my 2c.