oachalon, The RX-V1400 has plenty of power for your speakers. M60s are very efficient. If you had watt meters, you'd see 0.1 watts (yes 0.1) is pleasantly loud, and 1 watt is very loud. That sounds impossible, but it's true.

You'll get vastly more audible difference by getting a subwoofer, or a multichannel SACD/DVD-A player and some multichannel high-res discs.

As a side benefit a powered subwoofer will further offload your receiver, as most power is spent on bass frequencies.