Upgrading Tube Preamp from Audio Research LS-7 - Recommendations for better soundstage?

I want to replace my ARC LS-7 tube preamp. I fell in love with the bloom and warmth when I bought it. But it doesn't have the soundstage focus or width that I had heard from others I had demo'd at the time. I think I want both now!

Any recommendations on upgrades? - tube for sure, but something with better soundstaging - more focus and width. Open to used gear like an ARC SP-16L or Prima Luna Prologue or Conrad Johnson Classic or PV15 or Rogue 99 or??? These are just some I had seen used in the $1000 - $1500 range which is basically my budget.

Don't need a phono amp but would use one, don't need a remote but would use one.

My system.
- Digital and vinyl sources
- ARC LS-7 Tube preamp
- McCormack DNA-1 solid state amp
- Martin Logan SL3 Electrostat/dynamic woofer

Thanks much.

Those are some great suggestions. Ones That weren’t on my radar. Been wanting to venture into new territory. Thank you all very much. The hunt begins. 
Have you read about the Don sachs model 2? Have you read the preamp deal of the century thread regarding the Supratek preamps? I'd add those to your list for your consideration. Both are very highly rated custom made by hand products from very small companies, So they don't get a lot of press.
Well I found a UltraVerve 3 with remote and lots of tubes to roll. Should get it Friday. Thank you everyone for your great info and tips. Truly appreciated.