Will VPI's Classic 3 sound much better with a SUT?

Your Fosgate has 60db of gain. Enough  for most of the popular MC carts.

Former owner of  one for 12 years- great phonostage. Get a different  cart for a different  "sound" Also a longtime VPI Classic user

If you're  seeking  dramatic improvement dump the VPI/Fosgate and open the wallet wider. 

You will hear less tube rush at high volume with SUT-MM setting if you're the type that listens for it.

Needless expense, IMO.

lewm: Your math is off! The Fosgate mc stage amplifies the signal about 10X. So .3 mv becomes 3 mv. That is enough for a typical phono stage. You didn't figure in the gain of the Fosgate preamp's line stage. Most line stages can output several volts. Plenty to drive power amps, which typically need 2 volts for full output.

Jason, I don’t know where to begin. But 60db of gain provided by the MC stage in the Fosgate equates to a 1000X voltage gain, and a 10X gain that you claim would be insufficient for any phono stage ever. 0.3mV multiplied by 1000 = 0.3V

Also, I didn’t figure in the gain from the linestage because I cannot find any information on that and because most integrated amplifiers don’t add linestage gain. So I’m guessing the linestage (which is probably just a volume control ahead of the amplifier input stage) adds no gain. To support that assumption I found that the UR has only one tube that drives its mosfet output stage. That leaves no gain device available for any sort of linestage gain.

No need to spend $1750 on a Bob's SUT! I have five SUT's. My Bellari is a favorite! Only $350! It sounds excellent with my Denon 103R! 

The typical mc stage magnifies a mc cartridge voltage by a factor of 10. So .3 mv becomes 3 mv. Adequate for the typical phono stage, which I assume the Fosgate has. I am sure the Fosgate line stage can output several volts. So plenty of volts to drive a power amp.