Choosing between 2 preamps

I'd pass on both and consider the Audio Research SP-14 that's listed on eBay right now for $1400.00.  Especially since you have an Audio Research power amp.

I don't have a horse in this race, and I'm not getting anything from the deal, but this sure looks like a great deal on a preamp that's definitely top-tier. Stereophile said 

'In my opinion, the sound of the SP14, via line or phono, will set new standards for the industry. I can see other companies using the SP14 as a benchmark by which to judge their own products—it's that good. It is user-friendly and attractively styled, injecting its unique form of magic into the reproduction of music to a degree I've rarely experienced before. I feel it should be included in Class A of "Recommended Components." It is a very special product."

@honeybadgertube RCA to XLR cables are made. The only meaningful advantages of balanced inputs - improvements in CMRR - don't happen unless you're running cables over 5M. Even in RF noisy environments a properly designed shielded unbalanced connection simply don't suffer at short lengths. In a recording studio with hundreds of cables and RF intrusion opportunities, it's a different story.