build a M-ATX pc instead of a ATX one that way its small enough to carry around to LAN parties but still packs a punch.
a rough idea for you is this (the psu is a little on the large side but i could not find the old AX650)
the things you might want to change are the CPU if you dont plan to overclock, GPU if your an Nvidia fan boy, the case if you want something a little different and the RAM if you can find something faster MHZ wise in Dual Channel specs. also i never add keyboard and mouse because thats going to come down to what you like/want but if it was me id be looking at a mechanical keyboard with some cherry black or blue switches. you might also not need the 256gb SSD and may want to get the 128gb version to save some extra money but id keep with the samsung 840 pro series tho.
the screen shot list would be pretty much the way i would go tho depending on your ssd size needs etc