I've been on disability for a few years now, pretty much retired, so I'm of similar mindset. Get what makes you happy, after researching various tech sites, asking friends here and elsewhere, etc - sounds like you have a good plan and idea what you want to already cooking.
Regarding other games/sims, IMO if you get a machine that handles this game, it'll handle everything else pretty much out there (beta wise, even AH2 to a large extent with everything truly maxed). I don't think you'll find an online game better than this, but I do enjoy single player stuff, FalconBMS is essentially free and incredible for that (dynamic campaign still), and ARMA3 has very basic flight stuff with all the other types of warfare, and the helo parts in there aren't that bad TBH. That's a great one to waist retirement time on, but there are tons of others. Again, I doubt you'll find a replacement for what we get from AH, the only direct competitors for online quickly fade compared to this product. IL2 Cliffs of DOver with the free Fusion mod is great for some single player, but again, so far as multi, and especially massively multi, there is unlikely to be anything that surpasses this in my lifetime, if I was betting the farm.
Re: SLI - I too made the same vow, I've always bought SLI right back to the very first offerings, Voodoo2 12 meg SLI cards, and had the 680, 780, and 980/ti cards in various SLI combinations. If pulled the 1080 cards from all our SLI machines and tested the stuff we play with just one card - other than just a couple AAA type 3 day wonder type games, where the SLI profiles aren't bad - little to no FPS advantage. We're using 144/165hz 27" Gsync 1440p panels and one 34" 100hz Gsync - one 1080, not even overclocked, can maintain virtually every game at ultra close to or at max FPS. Overclocking the cards to say 200/450 or 500 almost ensures this. With the new 1080ti coming this year, I'll sell the remaining 1080 cards then (2 are gone now, just one SLI system left), and replace them with the fastest single card, be it the ti or Titan. No more SLI, ever, ever, again.