Actually two tips. First, if you want a giant desk just buy an unpainted door. Ta-da! 2m long desk for $100. Prop it up at either end with IKEA drawers.
Now, to make your cables neat. Buy a roll of Velcro, the stuff we use in data centres to neaten cables. Buy a bunch of small screws, 10mm is big enough.
Cut a piece of Velcro about 10-15cm long. Screw it, through the center, to the underside of your desk. Repeat as required.
Gather cables neatly, secure with Velcro, bask in glory.