need to increase wifi range/strength after moving to house

Hi all,

I am currently running an old linksys wrt-54gl that I've had for several years. We recently moved into a 3 bedroom house where the router is in a room on the bottom floor. In the bedroom on the top floor the signal gets rather weak (the way the house is set up, the signal looks like it may be going through a lot of drywall. It's not terrible, my wife's iphone looks to get cut down to about 50-75% of full strength, but my galaxy nexus gets down to about 0-25%...so I suspect some of it is the phone.

In any case I'm looking for my best solutions to get a strong singnal throughout the whole house. I have a low to intermediate knowledge of network engineering and products (I understand the basic concepts and have done some network based software engineering, but when it comes to issues of how specific product features compare, behavior in a practical setting like my house, how best to configure for speed/range with multiple devices on the network, etc) I am mostly at a loss. Here is some general info:

- I have several devices on the wireless network. Right now it's- 2 phones, 2 tabs, 2 laptops, PS3, 360, Roku2, and a printer. Obviously not all being used at once, but the phones, laptops, and ps3 are getting a lot of use throghout the day.
- Recently put dd-wrt on the router as some had told me that gives a better signal. It hasn't made much of a difference as far as signal strength.
- I've seen routers that advertise their range as the main selling point, but I'm interested to know if any of those are good routers in general or if I'll be sacrificing other qualities. Basically I'm wondering if the differences in routers out there will be negligible in solving this problem and if I should go with getting something like a repeater/range extender instead?

I think my router is generally pretty good quality and dependable based on my own experience and most reviews, but it's old. Some people say those old routers are better than the newer ones out there (with dual band, wireless n etc), and some say the newer ones are better. Like I said, I have very limited knowledge especially when it comes to newer products, so any help here would be appreciated!