This is a great question and the exact one that sent me on my last mission to upgrade the 2 channel set up a few years back.
For donkeys i'd been moving sideways with components and i was happy doing that for many a year, just enjoying.
I moved property and ended up having a nightmare with the neighbour, any noise above normal speaking which is around 50-70 db i'd get a letter from the council, totally unreasonable and we ended up moving, but thats another storey.
But because of this i bought myself a pair of Grado SR60. At the time (about 4 years ago) i was running a modest set up incorporating an Marantz PM6002 (i think), Arcam Cd 73 Diva and Epos 12.2 plus cables of different types and a TT. I plugged in the Grado one evening and had a great big smile on my face and enjoyed the music loud! After a while i started to get accustomed to the sound and when i listened to the set up i felt a bit underwhelmed. I wasn't getting the sound i had via the jack so the quest began in ernest to change that. I auditioned, saved, read about products on-line, saved and watched the usual places for suitable HiFi. And when i say suitable i mean at a quality gear at silly prices!
Over a time i had saved through working and selling stuff off and had a seasonable amount and come across an Chord CPM3300 on e-bay for £1700 no reserve (ideal candidate). Watched it for days and then bid with 6 hrs remaining (it finished early hours), i went to bed. I was the first and only bidder! Sweet! When i awoke in the morning i never thought i would had got it at that price, my maximum bid was 1750.
(Theres one on e-bay now for 3300!)
The quest went on in the same vein, with the speakers next a nice unblemished pair of Totem Mani II Sigs (1750) then a MF Nu Vista CD player (1000), some cables and this year a VPI turntable. It has taken me all that time to build up a system that out performs that spacial sound you get from headphones, but my is it worth it!