Is upgrading pre worth it?

Wow.. ok learning something here. NOW.. rogue has an the pre99 super magnum. that would be the equel to my st100. what would be a good soild state that might be better. IS it ok to mix solid state pre and tube amp of different brands?

kingdombuildingcon it's no problem mixing ss and tubes assuming there are no impedance mismatches or anything but I think, and others here too, that a tubed preamp is the way to go. In fact many do the reverse of what you propose and pair a tubed preamp with a ss amp. I would say unless you have some compelling reason to get a ss preamp stick with tubes.

The preamp is the heart of a system and absolutely required for an excellent system.  

In my experience, the amp makes a much bigger impact than the preamp.  I was using an Outlaw 975 as my DAC and pre and then switched to an Odyssey Candela and Schiit Bifrost Multibit DAC.  There was a difference, but it wasn't huge.  I then "upgraded" my Odyssey Candela to an Aesthetix Calypso Signature, which is 4.6x more expensive than the Candela.  I would not say that the Calypso is that much better.

However, when I upgraded my amp to a Sanders Magtech from Odyssey Kismet in Stratos monos, the difference was quite pronounced.  I'm running Magnepan 3.7's. YMMV

Let's just say it depends. Gerenally speaking, I advocate getting the source in order, then amp/speaker cables/speakers unit and preamp the last to bind everything together. In this case you match preamp to both amp and phono stage, and dac that you already got. It might be in the end the most important component - more reason to do it when the rest is set. Could be done differently, yeah.