I think I posted in this thread before about getting my 'home office' done out properly. I designed the layout myself and had a company build the whole thing for me. In total, it cost £1900 but thats because I went for fancy moulded doors with the oak finish, lockable draws and a few other features such as extra deep cupboards. The standard 'ikea' finish type of cabinets would have only cost £1400, which still isn't that pricey for a fully customised individual design and installation. If you are going to do something like this, find a local company as most of the national franchise companies we approaced quoted upwards of over £5000 for something that 'resembled' our design.
The pictures aren't the best as its not really possible to get a good angle on everything with it being a small room. Basically it's a 10 feet x 6 feet room. The desk top is one piece with space for a tower PC at either end. These also have a removable shelf inside them which mean it can handle big cases if needs be. The two Lian Li towers we use fit perfectly! The wooden side panel of the tower enclosures doesn't go all the way back to the wall underneath to ensure that warm air can move out from behind the PC and vent gaps and cable cutouts on the desk let it rise out from behind.
The desk is 750mm deep and about the same in height which is perfect for standard office chair adjustment. The drawers in the middle are lockable and have plenty of room as they go all the way back to the wall.
The cupboards and bookcase are also extra deep to give plenty of additional storage space for all the crap that seems to accumulate in small rooms!
Hardware wise, there are two PCs, the laser printer and the router and an Alienware laptop so yes, it can get warm in there when the door is shut.
Both my partner and I play games (World of Warcraft, World of Tanks) as well as both having the opportunity to work and study at home every now and then, so it's just really nice to have a comfortable 'executive' place to work from.