If you're looking at getting a 6ch radio, go for 7. There are functions the 7ch radios will do that the 6ch won't do, other than just having an extra channel. Two examples off the top of my head are dual elevator mixing and non-linear channel mixing (i.e. 'up elevator' with either direction of rudder input).

I have the Airtronics RDS8000 8ch radio. It's an unbeatable deal at $150 for radio and one receiver and $229 for radio and two receivers. Easy to use, comfortable to hold, and capable up to interediate->advanced levels of flight.