Basic router question

I am about to get wifi in my house so that we can connect to the Internet with more computers and laptops. However, I do not know anything about routers and when doing a search e.g. on amazon, thousands of routers come up, even if I only search e.g. linksys.
What should I look for? I googled it and read a couple o articles but it is still not clear. So far, I have figured out that N is better than G (although not necessarily). But what should I look at, when comparing these routers? Is RAM or 'flash memory' important? My house has two stories but it is a very old house so the walls are extremely thin (even the ceilings). What I would like is to have a normal speed internet connection at most spots in the house which is about 800 squarefeet on both stories. Mostly for just surfing. And money is a pretty important factor.

Thank you for your help in advance!

Are you having broadband installed for the first time from an Internet Service Provider?

Only asking as most supply a wireless router, preconfigured, which will get you started.

If not, are you getting broadband via cable or ADSL?

Sorry that I did not mention this in my first post; I already have ADSL connection.

Please could someone please help me out?

If you're just after router recommendations please post back with which country you're in and what equipment you want to connect

I'm in the United States and I would like to buy a router for my macbook and an old PC with Windows XP on it...

I would get an N based router. Linksys are ok, but I like the Apple one for the ease of use.

AirPort Extreme Base Station - Apple Store (U.S.)

linksys are usually lower quality, at least from my experience.

im not sure about the airport extreme, but i assume your going to pay extra just for the apple brand just like you do with everything. when it comes to the router you just need functionality not some flashy apple product.

i like netgear.

as for which protocol to use, that depends. not all devices are compatible with 802.11n. usually those routers are backward compatible with 802.11g/b. so usability is not a problem, its just that your paying for higher speeds you might be not able to use. if you have devices that can utilize a 802.11n signal then go ahead and buy a "n" router. or buy one anyways in preparation of the future.