what receiver to get?

[Sir Terrence the Terrible]

i guess i'm wondering if there what the pros are for the 7.1

Is the only difference the 2 additional channels? and if yes, is it worth it for me to get the 7.1 just to power that mid range speaker (the speakers have 4 sattelites, 1 sub, 1 midrange)?

I would always go for the 7.1 unless it is a noticeable step down to a good 5.1 channel receiver. A 7.1 receiver can playback all of the 64 7.1 Dts and 36 7.1 Dolby TrueHD Blu ray soundtracks that are out there - a 5.1 receiver cannot. If you want a deeper rear soundfield, then go for the 7.1 receiver. If you couch or listening position is against the rear wall, then a 5.1 is your only choice.