I agree that if you're not balanced from start to finish, then you're not balanced so no need to worry about it. Just connect your pre-amp output to the 1/4-inch inputs either with 1/4-inch adapters to standard RCA cables or readily available cables with RCA phono males on one end and 1/4-inch males on the other. I have 4345s and bi-amp them using an Ashly crossover and that's what I do. Now my Crown amps take 1/4-inch inputs so that's a bit easier as I just use 1/4-inch males on both ends of the cable from the crossover to the amps. Here's what I use when I have to go RCA to 1/4-inch and they've worked well for me with Crown amps for years in non-bi-amp systems: