i actually got that desk free. a local retail store was throwing it out (an old clothing display table). i just put formica on the top and now it makes a nice 7ft wide 2.5ft deep desk
the box you called an amp is actually a receiver which is meant for home theater speakers and systems and generally most of them are about that size. headphone amplifiers for headphones are much much smaller. perhaps 1/4 the size of the ps3 slim.
as for equipment you can hover over my avatar and it will show a list....but...
pioneer vsx30 receiver $550
klipsch quintet iv 5.0 satelite speakers $500
klipsch sw450 450w subwoofer $350
speaker wire, wall plates, bananna clip ends $100-150
i did not need to go so high on the receiver but it had functions that i wanted which made setup easy back before such things were common. generally my system is only considered at the low level when it comes to serious hifi home theater as many budgets for even low end setups are at least double mine. for the record i would have loved to have bookshelf speakers but they are much much more money.
its quite possible to make a decent hifi set for much less (energy classic take 5.1 set + receiver can be done for about $500-550 total) but i liked the klipsch speakers so i went with them and at the time i had some cash from extra overtime to spend on such things. when you consider the cost of things like televisions (which often cost $1000+) computers (again which often cost $1000+) game consoles (often $400+) and various other connected devices dropping $500+ on a good surround system really isnt much at all.