There are many access points out there that will give you good range and good performance. I use the DGL-4300, and it covers all 2500 sq ft of my home (5 bars everywhere), and its never had a problem with connection all the computers together and keeping them connected.
There is also this one:
High Output Wireless Access Point - Bridge
This router is really powerful, and will give you the maximum range that an wireless access point could possibly give. I've never used this router, so I can't say how well it will perform, connection and stabaility wise.
If you decide to go with a router which isn't as powerful, you can buy the Hawking signal booster:
Hawking Technologies
Borgslayer