I have no doubt that it likely depends a lot on the type of effects you are using. And I can't see why having a good quality amp would not make it sound better. But I have a crappy old Fender Chorus amp that has been moved across many states since the 1990s when I bought it and is in need of repair to get rid of noise and other issues. So right now my best choice is to go direct into the Tascam.
However, as I mentioned, I have used it with Jangle box and Wah and it sounds very nice to me. With my Ric 360/12 I like to go for a bright sound (ala Byrds), but I suspect it might also make a difference if I wanted to go for a more warmer sound, esp from a tube amp.
I just purchased Electro-Harmonex' "Talking Machine", "Mel9" Mellotron simulator and "Synth9" synthesizer simulator pedals, delivered about an hour ago.
I am testing the Talking Machine now. Its very cool and has good sound. However, as I said, it likely could be improved going though a good quality amp, but I am very happy to use it as it is.
If I find anything I don't like regarding the Mel9 or Synth9, I will post again.
Best,
Stephen