+1 for the Algor too; if you are lucky enough to get the chance to buy an Algor, you get flash ROM a la KickFlash, plus 3 USB ports which work fantastically with Poseidon.
It has to be one of the best cards in my A4000, it makes bootups quicker as it doesn't have to reboot to load in the updates. I have a heavily modified Kickstart which includes all the 3.9BB2 ROM patches as well as some third party hacks and patches. If the Kickflash allows you to do this, by all means RECOMMENDED. :-)
Good luck with the A4000 project, by the way. I had an unbelievable amount of fun building mine, and I won't be too quick to look back to an A1200. :-)
There are only a few finishing touches I'd like for mine, a proper cooling solution, a Cocolino, and maybe one day a sound card. :-)