Do you think I should go for a Sam440 or spend extra and get a Sam460 instead? Also, I have no interest in MOS :/
I'll give you the same advice I left you at aw.net, go with the Sam460/AmigaOne 500 especially now that you can gain a free PCI slot and use the latest Radeon HD cards.
I sold my Samflex@800 over a year ago and even though it was a quick & reliable board to run OS4.1 it needed a few hundred more Mhz to smoothly run some AGA game via E-UAE, play videos, render dwgs in Blender/Lightwave quicker etc.