What is the power rating of your VT60? 60 wpc? Does the sound sort of peter out at high dynamic range or volume? Also, Is it a stereo amp? I don't know the impedence characteristics of your speakers. If they are difficult loads then you need a strong amp. But, if the sensitivity of your speakers is over 89db/1W/1meter, then there shouldn't be an issue unless the impedance does bad things.
If the VT 60 just doesn't have it, then any of the above mentioned amps should work just fine.
enjoy
If the VT 60 just doesn't have it, then any of the above mentioned amps should work just fine.
enjoy