I have a Zinky Supro Sahara 25 watt. I know it shares certain elements with the Blue Velvet. I switched out the stock Sovteks (I'm pretty sure the velvet uses the same) for JJ's, and it sounds great: way more focused with better clean headroom. As for the Speaker, I love mine to death, so I wouldn't touch it, but I'm pretty sure that the Blue Velvet has a different speaker, so it may be apples and oranges.
By the way, how do you like the Blue Velvet ? I've been eyeing them for a while now, but don't know anybody that actually has one. What are your thoughts?