Cartridge or Pre Amp

The current Tube Box DS has the ECC 83 tubes just like some of the higher priced tubed stages carry. I'm all for upgrading but I'm also aware of the diminishing returns on said upgrades. I'll triple check the DIP switches.
http://www.project-audio.com/main.php?prod=tubeboxds&lang=en

@almarg Agreed.  The Herron would be better matched to a preamp with a higher input impedance.  Keith Herron would be a good source to determine whether changing tubes in a VTPH-2a would overcome a lower input impedance pre.  

My initial post has the incorrect link. This is the correct one: Pro-Ject Tube Box DS

I didn’t mean to cast aspersions on the AT cartridges (as the happy owner of an ART9 myself). What I’m suggesting is that at this stage of the game the OP might want to be learning more about which parts of the system have the most leverage, and which kinds of effects, rather than getting lost in the wilderness of specific models and their various merits (as described on the interwebs). I guess it’s a version of the adage, "give a man a fish and he eats for a day, teach him to fish..." etc. First learn about the hinge points in the system and then make decisions about tubes, cartridges, phono stages and the like. I understand that it’s a bit of a Catch-22 because you have to make decisions about what to buy before you can hear the effects. But still - I’d say cartridge over tubes (if you have the disposable cash). I also agree that changing the phono stage could be helpful (and more important than the cartridge), but @joyofsound you did start out the thread by saying how much you enjoyed your new phono stage and its qualities.

The AT-ML150 is great, i've tried all cartridges from this series, for $350 the AT-ML150 is unbeatable! The sound is full of details, for double price the AT-ML170 is better. I've tried these carts with different phono stages from $500 to $2500, it wasn't dark at all. Zu Audio Mission Phono cable is great and you can buy one directly from zu audio promo auctions on ebay under $150.