pre-amp opinions

Sorry for the redundancy, I realize there are already a number of similar threads, however I'm in the process of switching from a ss pre to tube to specifically power AR REF 300MKII amps and was wondering if anybody has been up this mountain before. I'm awaiting a AR REF 2 MKII to audition, and know that is the recomendation of arc-heads, but I'm also considering others and am open to suggestions.I need balanced and se. Thoughts are appreciated.