thanks for a lot of great and welcome advice. Based on your tips (and some additional ones), I settled for this build for the time being.
Case Silverstone GD07
MB AsRock Z77 Pro4-M
CPU Intel i5 3570k
GPU SAPPHIRE Radeon HD 7970 3GB
RAM Corsair 8GB DDR3 1600Mhz
CPU cooler Arctic Freezer Xtreme Rev. 2
PSU CORSAIR TXV2EU 650W
SSD Crucial SSD M4 128GB SATA3 2,5"
HDD HDD CAVIAR 2TB SATA 6 Gbs
GPU might be exchanged for GTX670, depending on actual price, which I can get. Aiming for branded ones though. Components were chosen based on local availability, but will consider buying abroad.
Any final thoughts? Also, I want to control the rig with an IR remote (Logitech Harmony 1100). XBMC should be no problem, but I also want to shut down / power up the PC or at least sleep / wake it. I read somewhere that it is fairly simple story, I just need to get a simple IR receiver with remote, program Harmony 1100 and am good to go. I suspect there's more to it than just that, e.g. motherboard has to be fit for that. Do you have any experience which you could share? This is an area I have no info about.