What is a good HTPC configuration.?

There isnt an easy answer to this... it really depends what you want.

First thing is to decide what operating system / HTPC software you want - once you know this then at least you know what hardware will be compatible. I have an HTPC system at home and use Windows 7's Media Center. This allows me to have networked X-Boxes in all the rooms where I want to watch TV. So... I fitted it with 2 x dual TV tuner cards - so I can watch and record 4 channels at once. If you go down the Microsoft route I would go for a quad core CPU (Intel i5/i7), 4+Gb RAM (make sure you have a 64-bit operating system so it can take advantage of over 4Gb RAM).

Also make sure you have plenty of storage... I would suggest Western Digital RED disks as they are suitable for small NAS units so are pretty robust. The 3Tb disks are a good option.

Install the operating system on one disk (Maybe a 500Gb unit) and then fit the 3Tb disk as a store for the programmes you record / music / photos / movies etc - that way if you ever need to re-install the operating system you wont lose your multimedia!

Hope this points you in the right direction :)

I think there can be a bit of 'snobbery' over HTPC set ups. I've got an AMD APU A8. I've got a cheapy AMD graphics Card to try and use Crossfire, but it doesn't seem to make much difference. I've got 8GB RAM but again probably not needed. I'm running Windows 8.1 with XMBC. I do also sometimes use Hyper-V and connect to VMs from a laptop, I've got a very old 250GB SATA drive for boot, 2 old 1TB drives, and a new 4TB SATA.

I've a mate who had lots of success simply using old Corporate 'slim' desktops (very cheap on ebay), that he's checked support XMBC. They stream over wifi from a central server and are very cheap. They're running XP.

Basically you can probably use ANY PC from the last five years and it work. Most TVs will have a VGA input (with an audio input), but personally I use HDMI.