That RadioSpectral design is not a Panadaptor, it's a device you can install into your 7300 to add an RF takeoff to drive an external SDR such as the RSP1A and add panadaptor functionality. When I had a 7300, I installed the RadioAnalogue board and it worked well.
The original design was produced and marketed by RadioAnalogue. They contracted some Turkish guys to work on the design and production - the relationship broke down and the Turks set up RadioSpectral to produce a cost reduced clone. There was a legal battle going on between the two companies over intellectual property rights - since I sold my 7300, I rather lost interest. RadioSpectral reduced the cost by removing components and then claimed that doing so improved performance.
The attraction of either board is that it fits into the 7300 case without any modifications. If you want to maintain that advantage, you'll have to be careful with the construction. You can get similar functionality with the MFJ switch (1708?) but that is an external box...
Martin (G8FXC)