Many subs have option to receive low power signal (from interconnects) or high power (from speaker cables, in which case a built-in crossover sends the rest of the frequencies to the main speakers). This second option is less preferred as it involves extra steps/electronics which can muddy the signal going to the mains while limiting/stressing your primary amp/integrated.
Now that you mention using separate low frequency amplification, the need for pre-amp outputs is absolute. And the Bel Canto's limited power output (60 wpc/8 ohms) is no longer an issue, especially with the GedLee Abbys.
With separate power to subs and the high efficiency of the Abbys, I'd think hard about a small/sweet tube amp, as you'll be listening mostly to less than 1 wpc. And unless you're a headbanger you'll rarely use more than 10 wpc. With digital technology changing so fast, this year's DAC darling will be long forgotten in a couple of years.
I tried one of the new Arte Forma Susan (I-150) integrates and it had electrical problems (60 Hz and 120 Hz hums) almost immediately before it completely died after roughly 100 hours on it. Fortunately the U.S. distributor honored the 30 day trial period before dropping Arte Forma.
