Ehm... I'm back to see this old post because I'm finally buying my desktop/monitor and sorry, I lost some answer... Thank you again.

So, I have still to buy the monitor, the case and the GPU. Actually I just sent back a Benq GW2765HT that I tested just a little and only in FHD and now I'm not so sure is a good idea to play FHD full screen on a WQHD (2540) monitor, but I'm afraid the size 27" was right but maybe to big for a FHD, maybe too small for a 4k.

@bintsmok: my very first idea was an ultrawide, but while probably very nice on game, I have some doubts with the other usages, the vertical 1080 it is what I found specially "little" on a FHD. And I'm not so sure I need the extra horizontal space but maybe can be nice as well. I never tried so I'm more afraid to make a mistake.

IPS vs TN, resolution, frequency, freesync... I'm very confused! But at the end is just a monitor, something I'll buy I guess :)

Just a question for the GPU. The radeon RX are now back on the shops and some are on ebay (mainly sapphire nitro), I think I'll try to go with a RX 480 that uses less energy than the 580. What about the memory for example in WQHD, are 8 GB useful (now or in the next few years) or can I go with the 4GB?

Just an update, at the end I bought an RX 570 and a FHD Monitor with Freesync (also on DP), just added to pc info ;) Thank you all