Belles 150A Ref Mod ?

Careful. Mercedes rims on a Toyota doesn't make it a Mercedes. Though it made handle better. These caps have received a lot of good press. They will sound different. Better is for you to decide. The designer of the preamp and amp designed them at a price point AND for a certain type of sound. It could sound worse. One better ingredient in the stew doesn't necessarily make for better soup. I remember years ago replacing resistors in my CJ preamp with Vishays (they were the rage then). It was way more transparent had cleaner highs, etc. It no longer sounded like a CJ and wasn't as musical even with the benefits. I have also done some cap changes on equipment, and it made them sound better for the most part, but sometimes not, as you need to experiment which can be costly. Hopefully you will benefit with Vcaps. I do know that the Belles Ref. amps are some of the best out there. Not sure if modifying them would bring great improvements. The down side is if you go to sell them you may take a hit since they were modified.