I've always asked myself the question: Why? Add a graphics card and a sound card, and you've got a PC with a 680x0 CPU. Not cool 
Keep it Amiga, guys 
That is an interesting subject.
Take a 'virgin' A1200, ok it's a nice retro computer but you can't really do much with it so you and some FASTRAM then a faster CPU, CF hard drive and an Indivision AGA with a chunky graphcis mode etc etc.
How far do you take it before it's no longer a retro classic Amiga?
Mediators fall in this category for me, stick a 1200 into a tower and add PCI video/sound cards and it becomes a slow PC that can't run PC software.
Personally, I'm happy that my 1200 is a classic as long as it is still in the original case, uses a 68k CPU (even if it's FPGA based) and can
natively run classic software.
PPC cards for classics are also a waste of time because (apart from the lack of software) that much power is pointless when tied to the original chipset.
