By 4-color do you mean process color or simply 4 pantone inks where you have a bit more latitude?
I also was intrigued by the AB Dick 3000, 3500, and 3500 S stream fed presses. "vintagestudio" sold a dozen or so of these 3000 and 3500s on ebay this last year. (the 3500 adds on-the-fly registration skew adjustment, etc.) The common comparison is between these AB Dicks and the Ryobi 3302, with some parts-availability edge possibly going to the Ryobi 3302. I thought these might be a good way for me to get my feet wet with process color offset coming from all-digital color, but I fear they are not up to the task of easily producing magazine-quality process color work. But I would also like to hear from anyone with direct experience working with these presses and pushing them to deliver quality 4-color work.