Hi,
The H/K 630 and other H/K receivers will drive the 6-ohm QS8s with no difficulty. In fact, H/K is one of the few brands of A/V receivers that I recommend for our M80 towers, which are 4 ohms.
By the way, you don't have to "match" the impedance of the speaker to the receiver. Any brand of receiver will drive 8-ohm or 6-ohm loads with no problems. It's only low-impedances of 4 ohms that may cause overheating, or protection-circuitry shut-down with some brands of receivers. But Denon, H/K or new NAD receivers will drive lower impedances in most cases without problems or current limiting.
Regards,
