I have two 604 models and the V69. The 604 is like the 603 except with a pad and a low cut.

I did a mod to one of mine that swapped out the cheap caps for Panasonics and the difference was pretty big. It really took the edge off the highs. I left one stock and it sounds good as well, but I'll probably mod it.

The V69 is really good. Spend a couple bucks and put a good 12AT7 in it. Groove Tubes are good and are cheap. Some people spend a few bucks for Telefunken.

Note - the 12AX7 is not the same as the 12AT7.

I also had the MXL 3000 but it didn't do it for me.