As indicated above, moving to 7.1 later is always an option. Also, if you go later you can get a good 2 channel amp, put it on the mains for times when you only want stereo and hook the 5 channel to the rest.

I'm using 6.1 on a 1050 as preamp now and the extra back channel adds a lot IMO.

I guess that would be an option too - you could find a good 6 channel amp and just get one more speaker.....