The foundation these guys came from, I have built a couple of the 50W PA and the matching ATU, the design started off as something from the ARRL 50W competition a couple years back. So given the community it had a pretty rough/strict peer review, if had not been any good would have failed on the spot.
I have seen the Mezzanine QSK board from the project used in a couple of QRO PA projects as well. Anyway their latest offering for fans of the soldering iron building kits as opposed to the screwdriver only which is the way some have gone has jumped over to kickstarter.
HobbyPCB is offering their RS-HFIQ 5W SDR on Kickstarter. They are offering a bare PCB for $30 which is probably about as cheap as it gets (I have bought one) if you want a board fully populated and assembled they are there too (honestly not the cheapest ever at $239 for something assembled but certainly worth a look)