Best Value Line Stage Tube Preamps?

Given they are all multi-input, multi-output, balanced line stage tube preamps, what are sonic benefits of a serious Rogue RP-7 or Prima Luna EVO 400 vs. the $899 Schiit Freya Plus?

FWIW none of these here support the balanced line standard. The standard was created to eliminate problems with ground loops and artifacts with interconnect cables. Not supporting the standard defeats this purpose!
The standard is fairly simple:
1) pin 1 ground, pins 2 and 3 carry the signal
2) Ground is ignored and not used for anything but shielding!
3) the balanced device will be able to drive a low impedance load- typically 1000 ohms or so.
These last two items are the meat of the standard. One myth about balanced operation is there is only a benefit with longer cables. While it is true that running balanced you can easily go 100 feet, you still get a benefit even if the cable is only six inches.


Once you hear what a properly set up balanced system brings to the table you won't want to go back.

atmasphere

Given that very helpful clarification, what would be your optimal components for a balanced line electronic chain (source - preamp - amp)?

Check out "Space Tech Labs". They have many different components and can even build custom if you want. The owner will answer any and all questions you have, even give you recommendations.  Tube rolling is great because some of his preamps can take hundreds of different combinations. The one tube that make the biggest sonic difference in his design is the rectifier. Changing a single tube for rolling a totally different sound is nice. Another thing you notice with his design, he uses output tubes in his pre...el34 up to kt100. This give a big open sound. I run one of his balanced preamps into active ATC speakers. 

Active speakers not an option in my main system. Nor tube preamps in my secondary system. But I do get the idea, also why it could work for those otherwise situated. Very interesting about Space Tech. Need to read up on that, thanks.

Given that very helpful clarification, what would be your optimal components for a balanced line electronic chain (source - preamp - amp)?

Optimal? The sky is the limit...

I prefer analog, and since all cartridges are balanced sources, I would probably choose a Technics turntable with a custom plinth, equipped with a Triplanar tonearm...

Do you plan to replace the amplifier as well?