In reply to:
I have no idea when it comes to setting crossover frequencies, and I have no idea how the subwoofer connects i.e. if it has its own crossover, does this mean the LFE channel will be partially output via the M3ti's?
Welcome, mr_rodge!
I love the international aspect of our hobby, and am always pleased when someone from another country pops in. Every now and then I pop in over at
AVForums which is in the UK, to see if I can learn something, or be helpful to someone else.
Now, to your above question. Your receiver has a group of outputs, just above the front speaker connections, labeled "PRE OUT." You'll notice one of them is labeled "subwoofer." With a powered subwoofer, like Axioms, or Hsus or SVSs, which have their own power amplifier built into the subwoofer, you simply run a subwoofer cable, with RCA plugs at each end from that subwoofer output on the receiver to the appropriate input on the subwoofer. This means you will be utilizing the crossover in your receiver as opposed to using the crossover in the subwoofer. This is the desirable setup.
I see that your receiver has the option of sending the LFE to either the fronts, the subwoofer, or both (Page 64 of your manual). While you are without subwoofer, I would recommend setting this option to FRNT. Doing so should do no harm to your M3s. But, until your subwoofer purchase, just don't expect much LFE to come out of the M3s. When you add a sub, set this setting to SWFR.
As to the crossover setting (also Page 64), you have a number of options. The M3s are rated +- 3 dB down to 60 Hz. I'd start with the crossover set to 80 Hz. If you wish, you can try 60, or 90, or 100 Hz to see if you have a preference, but I think you'll find 80 Hz will be fine. It is the generally recommended crossover point.
I wouldn't worry about "overpowering bass" with music. You control the volume of the subwoofer, and, if you wish, you can lower the volume, or turn it off altogether, when listening to music
