I pretty much agree with amigadave, though the mediator might be pricy if you don't already have a tower for your 1200. I've upped my 060 1200 to a mediator+tower, and haven't been happier with her! Though she does lose a bit of the console/wedge "charm" in the process. (A guy nearby my house craigslisted an A1200 that he wanted to save from the dumpster during spring cleaning, so I really lucked out on that)
Unfortunately, aside from a passing tinkering with AROS, I can only speak for the mediator, which has allowed me to use old PCI cards that I've gutted out of computers I found on the curb. (I'm not kidding here, when Vista first came out you would find old AMD Athlon/P IV grade computers all over the place on trash pick-up) I'm using a 24-bit card that I gutted out of the one on 2nd st., a sound card I found one Monroe St, and I'm not sure where I got the 100mbps card from.. Still have one slot to fill, not sure what to put in there yet....
Anyway, the performance boost was about the same (emotionally) as when I first installed my 1260 card and ran Frontier Elite II on it. MP3's take alot less CPU time, though I'm still considering getting a delfina for that. (Unless there's a PCI sound card w/ mpeg decoding that mpega.library/Amplifier supports) And the switch from a 10mbps PCMCIA to 100mbps PCI card is incredible! (Though deceptive in part due to Ibrowse/AWEB/etc... not needing to fight FBLIT for CPU time anymore, however straight downloads go faster too.) If you do get a Mediator and use GFX with it, I'd recommend a monitor with 2 inputs on it. (If you use AGA for games and stuff, keeping in mind the NTSC/PAL VGA difference, might still need a scandoubler if the monitor won't take 15khz hsync. A flatscreen TV with a VGA port would be about ideal if a scandoubler is too much, also keeping in mind the Mediator mailing list just announced HDMI/DVI drivers for GFX cards) A VGA switch+scandoubler would work (which is what i have now), but results in desktop clutter.
Sound cards are OK, though I can't really tell the difference between the AHI output when switching between the SB128 drivers and 14bPaula drivers. (Though I'm half deaf according to my wife, there may be more truth there than her being annoyed at me nodding and agreeing with her whenever I'm busy with something. :-D)
With the 100mbps cards, they're nice, but the drivers are REALLY picky. I have 7 or 8 of 'em lying about, and tried all of them. None worked. I ripped the one out of my fileserver (Basically one of the forementioned "curbside specials" loaded with hard drives, a VGA card, an NIC, and an NAS Lite boot floppy) and it worked. (I then had to swap NIC cards in/out of the NAS Lite server until I found one that worked with that....)
I've looked at the Morphos screenshots, they look nice, but I really don't know enough about Morphos to make any recommendations. Looks like it could be fun to play with, though.
What expansions would you need for AROS capability? (I've managed to install it on an old Thinkpad 390E laptop, works pretty well there. Though not the latest version for want of a DVD rom in the thing) Aros is alot of fun, has most of the more recent browsers ported to it (I believe, OWB, netsurf, etc..), and seems to combine the lightweight nature of AmigaOS with the horsepower X86 stuff can crank out, while eliminating the emulation "middle-man". (Though has UAE available I believe) I've not played with it beyone tinkering with the included demos and OS itself, though.
Personally, I wouldn't mind having a SAM, but I wouldn't be willing to hock my classics for one. :-D
Another thing to consider though, especially if your Amiga is still in a console case, would be a SubWay card, at least allowing access to USB devices. My wife especially appreciated me doing this, because she can still play Mahjong while I download pics from my camera. (And yes, she knows of the Amiga Mahjong clones.. I had to download every one I could get my hands on when her computer decided to fry her memory. Luckily it ONLY fried her memory....) Though this would only be useful if you use alot of USB stuff. (Like myself) I've gotten this to work with my wireless mouse (though I still prefer to use a mr. mysza ps/2 to Amiga + ps/2 to usb mouse adapter for this), a keyboard, SanDisk Cruzer 8GB thumbdrive, Sony Clie PDA, Kodak LCD picture frame, Netxtar (generic) portable MP3 player, and a SAMSUNG Digimax A503 digital camera to work. (though the clockport that SubWay plugs into is a bit slow, some patience is required).
Anyway, it is your money, and it really depends on where your interests lie. You have a rather fun lineup of ideas there, at any rate. :-D (And my wife isn't talking to me now, because after reading your post I asked if there were any Mac Mini's in craigslist.. hehehe...)
