Honestly I can't for the life of me understand why people don't flock full steam to SSDs. Ok, yeah their capacity may seem a bit low, but I can slap my OS on a 70 gig one for like 60$, and all my games/programs fit on a larger one (120-240 gigs) for like 200$.
As for everything else? Store it on a NAS drive/external hard drive. Internal platter drives make very little sense to me anymore for gaming PCs, or...really any PCs. The computer itself is streamlined for gaming, and when it comes to media I need to access it with other computers at a moments notice. It's better to keep media on a seperate system and just have the gaming system for gaming.
Also I don't get why people think that they need to upgrade so often. My build has lasted since 2008 (maybe longer). I've replaced a couple parts here and there as they have broken (HDDs->SSDs, GPU broke, technically I downgraded it), but that's about it. Any game I want to play I can play on high res.