I bought the Ampeg PF-20T as a silent practice tool as I cannot use speakers in my apartment. In particular, I run the output of the PF-20T into a Two Notes Torpedo C.A.B. to simulate a mic'ed 8x10 Ampeg cabinet, and from there into an Ampeg SCR-DI, which I use as an audio interface to connect headphones and MP3 player.
I must say that I am very impressed by the tube sound of the amp and it fully satisfies my expectations. The 3 band EQ is quite sensitive and allows to dial in a broad range of tones suitable for jazz/funk/slap/rock sounds.
One worry I had was concerning the 0dB input level as (in contrast to the PF-50T) there is only one input socket and I mainly play a MM Stingray 5 with active electronics, whereas most of the reviews/videos seem to have been done based on passive bass guitars. While it is still possible to get clean sounds, it is true that the sound overdrives fairly quickly, which means that it may not be the right amp for those who primarily want clean sounds.
Nevertheless I love the amp and therefore gave it an overall 5* rating.