Some of those external boxes do not support the 24-bit AGA modes. I don't have any experience with the one from Australia, but the price sure is attractive. The one on eBay right now for $100 though (white box with screw adjustment), I used to have on my A1200. I didn't care for it at all. Too much, what looked to be, RF interference, vertical lines running through the screen AND that fringe distortion on the left had side of the screen seems to be "normal" with those particular FF/SD's.
Indivision is about the best modern solution I've seen yet. From what I've used, only the Phase 5 video card combo boards best that one, but you're going to pay more getting one of those into your system than Jens' product! :lol: