When you do gaming it needn't be in extreme mode to DEMAND from the PC sources to give all. What happens, is I find gamers don't back down from to be slower or settle for less than capable. Gaming tends to push a PC into limits or prolonged play causing the PC to be "stressed" until the weakest link finally gives in. Regardless, if you don't play that much, playing games will always be in the "want" column of usage. The less you play will keep the PC into longer life cycle, hopefully. It's like driving the family van at NASCAR every other weekend w/o special prep other than changing the oil.
Money???, well you have to figure your budget. Let's be clear here, only you know what you can afford. That said, finding a "budget PC" is easy, buy in your range. If it so happens to provide all you need, then great if not, sorry. If it fails because you paid x-amount because in real usage you wanted a top x-amount result, just realize that. And yes, only you know what it takes to do what you need it to do. Unfortunately, I can advise on cost and find ALL too often the cheapest PC gets brought, when maybe for $100 more it really would have been more assured and yes it comes to that. I suggest you shy away from OEM brands because if you plan to upgrade or boost it's level of performance may not be as easy as a more generic DIY type PC, that just lends itself to upgrades. A decent mtrbd. alone costs $200+ and that's w/o the cpu. You can see how costs add-up but in the long run see a better and more user friendly PC to maintain. I suggest you review what a DIY website offers and compare that against any OEM builds. Use Amazon, Newegg, CyberPowerpc, Alienware, and DigitalStorm and just check what's inside the PC to compare. Dell and HP offer more intense PCs as well, but don't look for bargains, maybe returns(refurbs), etc. for resale.
As for Win8, it's better for tablet or typical non-desktop type, IMHO. It's still too new but if you want it, then get it. I find win7 delivering quite well and really win8 hasn't impressed me at all. Check websites, for "opinions" on that topic to get a feel of it all. Understand, if it runs great in win7, you can at a later date upgrade to win8, but that's up to you, now or later sorta thing.