There may not be much difference in the circuitry between the SE and SEI but with the SE being mono blocs and the SEI being an integrated, my guess would be the SE monos would sound better as they don't share a power supply or chassis. The other advantage (if you want to call it that) is that you can choose your own preamp when working with power amplifiers vs integrated amps.
Preamp Noise with High-Efficiency Speakers
I have Avantgarde Duo Classic Speakers, I hear a very audible buzzing noise whenever I insert an analog preamp. If I run my DAC (AMR DP-777) directly into power amp, the noise disappears. I have tried 4 different preamps (tube and SS), 3 different amps, a bunch of RCA and XLR interconnects, the problem persists. I have tried dedicated power line and two power conditioners (with Multi-wave options) and various high-quality power cords, so far nothing works, and I am forced to run DAC-direct into power amp. The buzz is not very loud but certainly audible enough to be annoying. There's no noise running the same equipment and power source into regular speakers, I am pretty sure it's just the Avantgarde (104dB sensitivity). Please share your solution if you have had similar situations. Thanks!