I have an Amiga 1200 with a Mediator SX board, but I also have a Apollo 1240 card instead of a Blizzard PPC, so what I write here might not be entirely relevant to your setup.
I put an Amiga 1200 with Blizzard 1260 inside a tower with a Mediator 1200 LT4. The full specs are at
http://retro-link.com/smf/index.php?topic=251.0The best GFX card that will work with the mediator seems currently to be the Radeon 9200 type of cards...
I have the Radeon 9250 PCI inside the tower, and it works like a charm! I'm very happy with it.
I agree with the rest of PanterHZ's reply,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcugThe Other Group of Amigoids
http://www.calweb.com/~rabel1/Southern California Commodore & Amiga Network
http://www.sccaners.org