IMHO and being and Amiga 3000 owner since 1991 and having tried about every possible combinations of graphics cards and setups. I would stay away from the picasso II and the spectrum cards, they are both fine cards but the Cybervision 64 is the best plug and play zorro 3 card for the 3000D. In normal use it is much faster than lower end cards and is has a path through. The Retina BLT Z3 fills the space between the picasso II and the cybervision 64. It is a real fast card, not as fast as the cybervision and it lacks a paththrough. If your going to spend real money get the CV64, it makes a much better improvement in useability and speed than an 040 card does.
The only reason I would install a Mediator Board is to get DVI out and higher resolutions, other than that I haven't found any other real advantage to owning one. The speed difference between a radeon and the cv64 is not that great really, running my 3000D on the CV64 in 1024x768 and the radeon in HD (granted it is a much higher screen) is pretty close in performance.
Again this is my experience with the 3000D. Good luck.
Really? I run the radeon in the 4000 @ 1900x1200x32 and i find its sits around waiting for stuff to do, way faster than the piv and cv64 which cant even do close to the same res. as a matter of fact those cards have noticeable slowdown at 1024x768x24 in my experience.
mediator is expensive but when you pay $1 for a 100Mbit card,nec usb card(modded) and such,$5 terratec 512i sound card... etc..it might make sense.It is more of a hassle to install and configure though. don't get me wrong i love z3 cards

CV64 all the way for the 3000 otherwise!