I think you really need to have a very well configured room to get the best of the LFRs.
Is my assumption about front presence vs LFR's correct?
I too will upgrade some day but I'd be tempted to use the LFR's and front presence, spread farther apart.
LFR's for music. I can't currently use 2 channel and front presence with out sending a signal to the rest of the 7.1 setup.
That said once I finish tweaking the room my M80's are in I'll be sitting pretty. They already sound really nice. The have a great sound field, like having no speakers most of the time (can't localize the sound unless it should be). I have had to walk up to the center to confirm if it was being sent a signal!
I personally love how you can keep turning them up and the quality doesn't suffer.