Not particularly familiar with the S series of Denon avr, usually look at X-3xxx series and up for the feature set (for example pre-outs and XT32, the 910 doesn't have a full set of pre-outs for example so you're limited to the on-board amps). As to whether the amp section will suit your speakers and desired spl we don't know since you don't mention just what levels you want to achieve. They're relatively sensitive speakers it seems (89/90 dB....from some looking around....which speaker series? is it S1, S2 or S3?) but may have some low impedance swings. I'd think at higher volume levels the avr could struggle in your setup. Try using this spl calculator to get an idea
http://myhometheater.homestead.com/splcalculator.html. Movie reference level is an average of approx 85 dB with allowance for 20dB peaks, and the LFE channel is 10dB more than that.
As to the 910 for $300...meh. You could get a
refurb with warranty of the 940 for $290.