Being able to display 95% of a colour gamut and displaying them accurately are two very distinct things.
Unless you plan on traveling with the computer a Laptop will be lower bang for the buck than a desktop. Unless, of course, you are buying a used laptop in stellar condition like this
one (sorry shameless plug for my classified).
PC's out of the box generally require greater video calibration than Mac's. Depending upon video card and monitor, PC's are all over the board with how they render a given image, whereas Mac's are far more consistent and tend to be more accurate. I've been using my macs w/o calibration and with excellent results, where as my PC are always needing calibration and I cannot get my three monitor pc setup to be consistent across the monitors. Which means that one or all are not rendering the image accurately.
The other plus with Mac is that you'll find yourself spending very little time fixing and maintaining your computer and the software tends to be far more stable.
Having said that PC's are cheaper even with a decent monitor calibration device attached. The Macs tend to have far lower cradle to grave costs in time and money, but higher initial cost.
A 22" monitor should be enough for a desktop and an HD 17" would be best for photo editing with a laptop. They nolonger make reasonably priced large monitors that have greater resolution than HD until you step up to a 27" monitor or larger. I use a 27" with my Mac, which I love and multiple 23.5" hd monitors with my PC.
WRT brand names. I haven't bought a prebuilt PC since the 80's. I build my own PCs. Prebuilt PCs tend to be encumbered with a great amount of useless software (referred to as bloatware) that tends to slow the machine down. Most new machines benefit from a clean reinstall of the OS which tends to be an all day project when you add in the installation of the software you do need.
If I were recommending a PC I'd look at getting one with the following specs:
Intel i5 or i7 quad core Processor, 8-16 gigs of ram, and 128-256 GB ssd for the OS and a 1 TB HDD for storage, and a mid rang nVidia graphic card. Extras would include USB 3.0, Gigabit ethernet, and a 1T external HD for back-up
I have not used Windows 8, but I can wholeheartedly recommend windows 7 Pro 64 bit. I would not recommend the home version and do not buy a 32 bit version. For myself and from advice of those whose opinions I respect, I would wait to buy windows 8 after the first major update (generally referred to as SP1).
The above machine with a 200.00 calibration spyder can be built with better components for under 1,000 USD (I just built my father essentially this computer for 800 with a cheaper monitor than what I would recommend). Expect to pay 250.00 or more for a 22-23" monitor. I haven't bought a PC monitor for photo editing in over 3 years so others could give you advice there. If you are buying a prebuilt machine, Dell and HP have a line of higher end monitors that, in the past, had a good reputation.
Having shopped in the UK and Europe, the 1450.00 USD machine described above would probably translate into about 1500.00 euros.
If you decided to go with a Mac a 21" imac would be in the 1,500.00 to 1,750 USD range and a 27" would run 2,000.00 to 2,250.00 USD. iMac monitors are factory calibrated and tend to hold their calibration (or least mine have). I don't know what the Euro pricing would be for Apple. As you might expect I would recommend an iMac. If you need a laptop a 15" mac book pro would run at least 2,200.00 USD and then I think you need an extra monitor which would add an additional 250.00 to 1000.00.
I saw your Mac. Nice piece... Goes for an option.