Hello EKanit. You have already made two superlative choices with both the Proac's and the ARC amps.Without any doubt, they are a synergistic pairing;and have been demo-ed together by both respective companies in trade shows and countless dealer showrooms around the world. For good reason I might add, as they never fail to capture the heart & soul of the music.I whole heartily concurr with Mr Wood's recommendation of the LS 5 mk3, as it is surely the logical choice and a really no brainer here considering the system mix .OH sure, there are many fine choices in preamps out there, however the common denominator here is the system synergy with the LS5 being as a known factor in the math. No trial and error anxiety here,no guessing game either. It just sounds right, the proverbial plug and play and forget about the gear. You may wish to roll the tubes to "voice" it in your rig in your room,however Mr Wood's choice of the nos russian military tube is another sensible and logical alternative to the pricey nos alternatives.That said: my experience with ARC preamps was strictly with the SP-series preamps sp-3a,sp-6b,sp-8 mk2 and the sp-10mk2 wherby the 8 and 10 employed the 6dj8/6922/7308 family of tubes in the phono stage as well.The phono stage of my SP-10 was just brutal on that tube, very critical to the quality of tubes for both noise and musicality in the phono stage. Replacing the 8 tubes was never any fun. The miltary 6hneb's or 6hnev's were a real godsend for sp-10 owners. Their line stages were never really hard on the tubes though and I don't believe the ls5 is either. It is actually the same general topology of the line of the SP-8 series. Hope this helps and all the best in your search.