Can I run a wireless g router and wireless n router at the same time?

[carl]

I have a wireless network in my home and I'm running an older g router. The darn thing has worked well for 3-4 years and is still going, and I paid all of $6 for it but I just need more range. All of my devices are g right now (work laptop, 2 kids laptops, Wii, wireless printer, Sky Angel internet tv that uses wireless connection). I am struggling with what to get to replace my aging g router. Seems like if I want to upgrade the kids' laptops to n I would have to switch everything to n which is not possible or get a simultaneous g and n router. I don't want to spend the money on a simutaneous router right now. So if I get a new g router with better range could I later add the n router to the network by running it on different channels and/or different frequencies so the g devices would run OK and any new n devices could take advantage of the n speed and range? Would that setup actually have to be two separate networks? Would an n router provide any better range even for legacy g devices? I would also like to set up my desktop as a sort of file server that the laptops could access wirelessly. Does that matter in terms of router choice? I also have cable telephone, would I benefit form a gigabit router to plug that into (It skips a little now)? I'm so confused! Thanks.