The OP said that he had already made his purchase and was simply trying to justify it. To that end, let me add the following.
Humans make most large purchases the same way: they purchase emotionally and then justify it rationally. This is not a failing, I just mention it as a point of fact.
When you're standing at the counter at your LGS or the table at the gun show, there are intangibles that you notice that may not show up if you are staring at a web page or list of parts. The fit and finish may look superior, or, in handling it, you may find the balance to be perfect for you. Even staring at a web page, you might read something that triggers your decision to buy that particular rifle. Whatever the reason, you decide at that moment to complete the purchase.
You initially get that rush of spending a lot of money on a major purchase. It feels good! When the rush wears off, all of a sudden "Buyer's Remorse" sets in. "Did I make the right decision?" "What if there was a better item that was cheaper?" "Why didn't I ask someone that knows more than I do?" And therefore the forum loads up with a dearth of these posts looking for support of their purchase. Again, there is nothing wrong with this as it is simply human nature.
You will notice that no one ever gets on the forums and says, "I just spent $2,600 (or whatever the going rate is) on a (fill in fully-custom brand you love) rifle and I'm not sure I made the right choice." That is because this is a best-of-everything, no-compromise item. The buyer has sacrificed a large sum of money to purchase the absolute best in the market. However, in today's economy, most purchases by middle-class citizens are a compromise because they can't afford a weapon equal in cost to four house payments! Therefore, either sub-consciously or through judicious budgeting, they pick a price point. They shop the LGS and Armslist and local gun shows looking for the perfect rifle at that price point. When one is finally chosen, the above scenario of buyer's high/regret/justification begins. Note that this goes away once a buyer has more experience with the same product, so you people that have more ARs than teeth no longer experience this. :-)
So, OP and everyone else in the same situation, here's the best answer I can offer: if it is your first time with this action/caliber/platform, only buy the basic weapon which you can afford, with the caveat that it be fully upgradeable. This will save money, making it easier to resell if you don't like it (for those of you who just gasped, Yes, there are those that don't like the AR platform and/or the .223 caliber!) but giving you your initial experiences with the weapons platform. As you shoot it and gain experience, add what you NEED, not what everyone thinks is the hottest thing. This is easier on your budget and your regret level. After a year of shooting and modifying, your wallet won't be hurt as much and you'll have THE perfect rifle - for you! Isn't that what you started out shopping for in the first place?
And for the connoisseurs out there, there is nothing wrong with multiple guns of the same caliber or platform as long as your budget and marriage can handle it! But you have to admit that you acquired these after you had experience with the platform and could make intelligent decisions based on your experiences. It is best for a new buyer with very little experience to have as little invested as possible in a large purchase until he knows what he wants.
So, buy what you are COMFORTABLE affording, budget for 500-1,000 rounds of ammunition, shoot the heck out of it, HAVE FUN, then make your own decisions as to what you need and can afford to modify or improve it. You will be much happier with no regrets.