Boy, the Eico was kind of a budget amp even when it was new- ceramic caps for coupling caps, cheap parts throughout... that would be a good amp to fall out of love with, and I would not abandon tubes on its account!
Tube technology has improved since the ST-70 (which was designed in the late 1950s); there are better filter caps, coupling caps, resistors, controls and there are better circuits. Even if your amp was refurbished it could easily be outclassed, even by other refurbished vintage amps like the Dynaco ST-70 or the Harmon Kardon Citation 2. But there are modern amps as you have learned that bring a lot to the table- its a big world.
Running out of the headphone jack of your computer is not the best way to get good sound out of it. IMO/IME you are better off with a DAC that runs off of the USB port and the appropriate software to make that happen (for example JRiver if you are running a music server). You very well could make good use of a good tube line stage since you are also running tape.
Tube technology has improved since the ST-70 (which was designed in the late 1950s); there are better filter caps, coupling caps, resistors, controls and there are better circuits. Even if your amp was refurbished it could easily be outclassed, even by other refurbished vintage amps like the Dynaco ST-70 or the Harmon Kardon Citation 2. But there are modern amps as you have learned that bring a lot to the table- its a big world.
Running out of the headphone jack of your computer is not the best way to get good sound out of it. IMO/IME you are better off with a DAC that runs off of the USB port and the appropriate software to make that happen (for example JRiver if you are running a music server). You very well could make good use of a good tube line stage since you are also running tape.