A 6,000 pound winch sounds awesome, but that's on the large size for our sxs I think. Sure, bigger is better - up to a point. Problem there is two-fold, and not made easier by the winch manufacturers, many of them kind of bury the figures and info you need. With a 4.5K winch, no-load free spool-in is on the order of 30 amps, that's quite a load on the battery with no load on the rope. Add load to the rope and current draw can go up over 200 amp. The duty cycle is (IIRC) something on the order of 1 to 10, depending on load - or 1 minute on and 10 minutes cool down. See: file:///C:/Users/bumpe/Downloads/Performance%20Data%20&%20Parts%20List.pdf
Having a bigger winch than needed may give one bragging (or pulling) rights, you might rescue a Sherman tank if you find one stuck in a ditch, but also maybe battery size issues. The typical aux battery may be 30 amp hours (when it's new and fully charged), enough to provide just a few minutes of winching at near full load. The 50 amp alternator only churns out that amount with engine at 5000 rpm, and not nearly a worthwhile amount at idle.
Just some food for winching thought. Oh, and wenching has an even lower duty cycle with pricy outcomes too.