Forgive me if I've offended - in this hobby, interaction is almost exclusively via internet forums, and what we can read/learn through our own experiences, what we read, and youtube, etc. I sometimes get a bit frustrated when people give advice to new hobbyists that may hinder the dissemination of accurate knowledge and that may not further the higher goal of even being here - spreading the word of the wet shaving lifestyle and showing others what enjoyment can be had from it.I've honed precisely ONE razor, so I can't say yay or nay to the 8K argument. If I tried to, I would soon be exposed as a numpty by the fine members of this forum with 1000-5000 posts. Some of them would even be polite.
Please don't read post count as expertise. Look at content and body of work before you paint with a broad brush.
Online, when learning how to hone, shave, strop, etc. and get the best shave possible from the tools we have to work with, we rely on the knowledge and experience of those who have more experience and knowledge than us to educate us. When I first started this hobby, I had difficulty trying to understand and digest the information that I was reading on these forums. Everybody had something different to say, what worked for one didn't work for others, etc. How was I to know what to do and how to do it?
Well, one of the issues with an easier learning curve is so much misinformation unintentionally spread by people who read much, but have little actual experience. Everybody here has their own body of knowledge to draw from, and everybody enjoys being included in threads and conversations. I and everyone here welcomes everybody's experiences and opinions, though occasionally, because of the very reasons that you quoted me on, some information will be given that might not be in the best interest of a new straight razor user/honer, and in this instance, it is the use of an 8k hone for finishing.
I'd like to reiterate that an 8k hone used correctly will absolutely give anyone a perfectly smooth and satisfying shave, and nobody needs anything higher grit than that. I would suggest buying an 8k naniwa. Does that mean that you can comfortably shave against the grain with an 8k every time? No. Does it mean that every brand of synthetic 8k hone will deliver what I just asserted? No. Does it mean that every honer will be capable of obtaining a shave-ready edge off an 8k hone? No. Does it mean that you can have a close, smooth shave straight off the rock every time, without extensive stropping? No. Does it mean that it is always as smooth and sharp as a 12-15k hone? No - but sometimes, yes. I'm just saying that it means that a stone with a true, actual rating of 8,000 grit can, in the right hands, with most razors, produce an edge that is satisfactory for providing a smooth, close shave. Again, I am not taking into consideration off-brand, natural, or unknown/untested 8k hones. I'm talking Nortons and Naniwas and kitayamas. I'm sure Shapton falls into there and some others.
And, because the OP was asking if, after spending $80 on an 8k hone, he NEEDED anything higher - I emphatically say NO - you do not NEED anything more to get a good shave. Others may disagree, but IMO, those who do are limited by their tools, knowledge, or ability. I would bet my life that if I sat down with any person who claimed to not be able to get a comfortable shave off an 8k edge razor, I could sit down and hone a razor with them, and produce an edge that even the most adamant dissenter would have to agree is a perfectly acceptable shaving edge.