MaSh, i'm not planning to invest more on the audio streamer, as i have to buy a decent DAC & a sub. So, the budget is to spend as less as possible, less than 10k. Current setup: iPhone 6S --> Musical Fidelity A1 --> Fluance SX6 Bookshelf.
I have the 3.5mm to RCA converter cable to play the audio files directly from the iPhone. I previously had SMSL SA98, recently bought an used A1 locally. The speakers were sounding neutral once, but ever since i connected them to A1, the sound is clear, more detailed but too bright and cannot listen for more than 30 mins. I'm planning to add a subwoofer as well in an assumption that it will warm up a bit.
Ahhh so it's not so simple. First, adding a sub will only add to the low-end, it will not change the signature of the sound. Second, if you feel just changing the amp, it has made the system brighter then adding a DAC or another component will not change the signature much.
You could try a simple Bluetooth receiver to start with, which would at the minimum help you go wireless. If that does not help much, you could try a warmer sounding amp such as Marantz, NAD, etc. Also, see if you can somehow EQ the sound a bit on the phone to suit your tastes.
MaSh