Hi Rustler.
Your PS Dac has from it's single ended output has 100ohms output impedance at 2.8v from it's "Resolution perfect volume and balance controls"
Your Spectron amp has 50kohm input impedance at 26db of gain.
These are a perfect match for each other to go direct with, and will give you the best transparent/dynamic sound you can get.
By putting a preamp into the mix you are just throwing money away to colour the sound with.
Cheers George