I'd advise against getting Mac as an "affordable" option unless you really
*need* it for porting software or something similar.
Mac mini is not really that great at all as a platform. Yes it's small and cute, but big fat ugly cables will be still sticking out of it.
Video cable, audio cable, usb cables for external devices, power cable. Then you trip over one of them and you got a flying Mac!
Really, there's a reason Apple designed iMac form factor and magsafe chargers for laptops - cable management (or lack of it). Mini's got none of that and really sucks in that department. It's also got crappy GPU (don't know about newest one though).
So, if you really
*want* a Mac then get a Macbook or iMac. Both are awesome pieces of hardware. My MacBook is by far the best windows laptop I ever had! Which says a lot about quality of apple hardware and availability of OSX software.
But if you want or need a small, affordable home machine, stick with the PC.
I've recently built my home machine with an AMD Athlon APU (quad-core, $60-ish new) and sub-$50 motherboard, also new. I've put it in a neat cube case(that's the biggest expense) and I have perfect little steamboxy home pc. It's not really an AAA gaming machine (Skyrim is playable at lowest settings on 800x600 res) but non-demanding games run flawlessly. It's my little DosBox heaven, that machine - yeah, I remember the 80s too!
Keep in mind we're talking about $150 CPU+MBO+RAM combo here. That's a full-pc for $250. CRAZY!
For $500-600 you can take one of those new cheap Intel Pentiums (wow, that just sounds weird) and Nvidia Geforce 750Ti and you've got better gaming PC than any Mac this side of MacPro will ever be.