I have: Cambridge Audio S70 speakers & Cambridge Audio azur 540A amplifier connected via phono to an M-Audio Fast Track USB external sound card, which is connected via USB to my computer. I would say that my amplifier and speakers are sufficiently 'warn-in', and I am using high-quality cables. The 'sample rate and bit depth' properties for the driver, on my computer, are set to the highest settings - '2 channel, 24bit, 44100 Hz (Studio quality)'. For practical reasons, I play most of my music through Spotify Unlimited, which streams (having emailed Spotify for official reports) "99.9%" of their music "at [and not just 'up to'] 320kbps", mp3. I understand that these files are compressed and will be of a lower quality than CD's for example. My speakers are located about 3-4ft apart from each other, at a slight inward angle. I am sat just 1-2ft in front of my speakers, and my reciever is located directly in front of my, under my computer monitor. My room is small-to-average.
personaly I would centralize the amp on the desk and place some bookshelf or nearfield monitors either side of it . which are slightly tilted upwards and inwards towards your ears. this will give you an improvement of sound quality that no change in anplifier will ever match.
So there it is, I recommend a new pair of bookshelf speakers. how much budget do you have.?