If you buy an amp "with phono", your only choice is an integrated amp. In that case you would be using the Decco as only a DAC, so you might just want to consider buying a good integrated amp w/phono and a seperate DAC/USB-DAC.
Ultimately it appears you want a DAC/USB-DAC, pre-amp, phono stage and power amplifier. You can choose whatever combination you want. All seperates, integrated amp +USB DAC, Decco + power amp and phono stage, etc.
Personally, given the need you have described, I would get a good integrated amp w/phono stage built-in and add a seperate USB DAC.
Enjoy,
TIC
Ultimately it appears you want a DAC/USB-DAC, pre-amp, phono stage and power amplifier. You can choose whatever combination you want. All seperates, integrated amp +USB DAC, Decco + power amp and phono stage, etc.
Personally, given the need you have described, I would get a good integrated amp w/phono stage built-in and add a seperate USB DAC.
Enjoy,
TIC