My intial thought is;
For what you want to do, the Vampire FPGA accelerator is what you want to consider.
At the moment the Vampire is only available for the A600. The A500 vampire is in development (soonish to be avaible)
Im unsure when the Vampire will be released for Amiga 3000 since development is a ongoing process. A wild guess, half a year from now, but thats a stab in the dark. The Vampire will restrict you to OS 3.9 tho.
The features of the Vampire core is also constantly in discussion and being expanded. There are "strong pressures" from the people in their IRC channel to develop a more modern ethernet feature, but the Apollo Team has to be careful about "feature creep" and cost.
So wether or not that becomes a reality is uncertain.
Anyhow, list a few Vampire videos and you can judge for yourself. IF it looks intresting you could join their IRC channel, and ask questions directly to the development team. If they dont respond there, the channel got quite a few knowledgable persons that will be able to explain the features much better than I can;
irc.freenode.org port 6667 channel #apollo-team
Atm the Vampire only got 128 megabyte of ram tho (for the moment).
http://www.amiga.org/forums/showpost.php?p=803680&postcount=34Comment by one of the developers.
Review of Vampire II
https://www.youtube.com/watch?v=lEjtc6JWlskAbout 1 minute 53 there is a Sysinfo test, altho its probarly not the best method of evaluating the performance
http://www.apollo-core.com/index.htm?page=performanceMore detailed info.
And then a few Workbench videos;
https://vimeo.com/152867182https://vimeo.com/152180575https://vimeo.com/153413790Ofcourse you will be "restricted" to OS 3.9 and 680x0, but then you will have hardware that is being developed and produced, at a reasonable price.
I realise you mentioned PPC and OS 4.1 too, but figured Id mention Vampire too, incase you havent paid attention to its development.