The Fosi monoblocks are indeed no miracle workers. For my desk set up they are doing marvelous. Notable is the stereo separation. The sound is fast and punchy. As for running 'running out of steam' there is no question of it. You could make steam with the amps, they become hot. I do cool them...
Finaly I did get my fosi amps. I connected the fosi"s at a small pre amp/dac from Douk Audio. My streamer is froam a raspberry pi with an Allo boss dac. It sounds great. The amps become pretty hot.
I did play for a long time with the hifiberry dac2hd. For me a big difference in sound was a linear power supply with a good power cable ( supra lo rad).
Iam on the market for a new streamer. For a couple of years I'm playing with a raspberry pi with an Allo isolator and an Allo Boss dac 1.2. The Pi is loaded with Volumio OS Premium. But Iam looking for an upgrade. On my list I do have the Volumio Primo and the bluesound Node. These are well...
I do use custom isolation feed under my speakers. I bought second hand IsoAcoustics Gaia III. I like them very much. In the past I did make feed from silicone sealant; very cheap with good results.