it's old news, but ''source first'' comes back to the bad old days of really low quality turntables. From there this idea seems never to have died.
Sure some dacs and transports sound a bit different to each other, but it's another league of difference to the effect of the room, the speakers position in the room and the actual speaker itself.
I think you're right to throw weight at this part of your system.
Heard the FB1's - not bad at all. I do think if you like what they do, then IPL offer a lot more for less money.
Consider the IPL 5 - a ribbon, ceramic mid and 10" kevlar transmission line speaker. £700 in kit form, probably about £400 if you pay a local carpenter to make them for you. I am currently using this speaker with it's original drive units and can say it's better than anything I've heard new that retails less than £2.5k
http://www.iplacoustics.co.uk/ipl_acoustics_____transmission_l.htm
Of course it's not the only pair of good speakers you can buy for reasonable money, quad 57's are the bargain they've always been for example, and there are loads more. I simply mentioned the IPL 5's because they're a ''lot more'' of a transmission line than the FB1's for less money.