Ray,
You ask two main questions, will the 6000 do or should you go for the 8000 Shimano OC. You’ve read the facts about dimensions and line capacity but also consider that the 8000 weighs nearly two ounces more that the 6000 so will it feel balanced on your rod? Another question to ask yourself is do I really need a reel that takes 230metres of .40mm line. .40mm is 20lb BS (or there abouts) so if you use either .33 or .35mm (12/15lb line) you simply don’t need the capacity. The other question you ask is what else to consider. I’m loathed to get into “my reels the best reel” argument because that a personal thing and purely subjective but for the record I use an Okuma reel on my Trent rods but I’m not fishing it 2-3 times a week in fact I only get to the Trent about 8-10 times a SEASON because of where I live. The smaller Shimano 4000 OC is my favoured reel on the rods I use on The Middle Severn, The Wye, The Medway and in the past The Kennet. As you start by asking about the Shimano models you are probably a Shimano man so I would say go for the 6000 but the spools will still need backing out or else you will have much line that won’t see water! See attached for data taken from the Shimano website.