Hi Classact,
If you already have a Rowland amp, then Aeris would be a better match as mentioned by Ricred, bearing in mind the limitations stated above. With DAC age measured in months nowadays, it may also be a hard sell used.
The Bricasti M1 has been described as a great performer in many threads here and does not have the limitations of the Aeris. Selling used would be easier.
What amp are you using now? If you don't have a preamp, you probably won't need one as both DAC's are designed to go direct to the power amp. As always, your mileage will vary depending on overall system synergy.
Cheers! J.