Preamp Audio Research GNS LS7 to LS15. Your view?

Is it worthwhile to upgrade from a GreatNorthernSound modified LS7 to a stock ARC LS15 with infiniCaps?

The additional remote is a bonus but not essential.
The GNS modified LS-7 is very musical with my Amperex tubes but I am just wondering if LS15 can go further.
Upgrading fever... I guess.

Any opinion is welcome.

Current setup:

Sony XA777ES CD Player
GNS modified ARC LS7 pre
McCormack DNA0.5 RevA power
DIY Scanspeak speakers
DIY interconnects
Cardas Hexlink Golden 5C SpeakerCables
My take on this is the LS-7 in it's stock form is better sounding than the LS-15. Look to upgrade someplace else.