Generally try to match impedances on both ends. If the 1/4" on the Behringer is unbalanced I would go RCA to 1/4", unless you find that the RCA to XLR connection has less noise. While keeping the amp close to the sub might have seemed intuitive at first, given the 25' run, I would also suggest keeping the amp close to the pre-out and running longer speaker cable. Very long pre-out cables should be avoided if possible unless you can go balanced on both ends. Doesn't mean your new cable won't work, but a general rule of thumb to avoid external noise.
Should probably mention that changing from XLR to 1/4" might affect signal level which would involve some recalibrating. After getting your subs dialed in you may want to keep the RCA to XLR to avoid that.