Just to play devil's advocate, contrary to the claim that an 030 is too slow for RTG software, most OS friendly applications don't actually hit the display hardware and will happily run on bigger, more colourful resolutions. I've used an 030 system with a Picasso IV in the past and it was certainly more comfortable than the native chipset for many older productivity applications.
However, the general observation that your machine will be too slow for more recent RTG software (ie, those that have been developed from the start with RTG in mind) is true.
I run A3000 w/ Zorro based EGS-28/24
Spectrum video card + CyberGraphx 4 software. This runs quite well on the original 030, 2/16MB configuration. Not sure what RTG software being referenced here but the stuff I use runs with little to no performance issues. I can only imagine that a PCI based video card would run as well or better + being able to claim some RAM expansion. Of course the 030 CPU will ultimately have a performance ceiling no matter what is happening on the video end.
The other comment about going Indivision route for this machine is good advice in my opinion. And less expensive than full blown Mediator setup.
