Get a dedicated access point, not a DSL/Cable modem with built-in WiFi.
Two brands I'd look closely at are Linksys (consumer grade devices that are awesome quality for their price) or Ubiquity (Enterprise-grade features at a consumer pricing)
Edit: You don't have to spend $150 to get a good wireless access point. Check this out
TP-Link AP200 Wireless Gigabit AC750 Access Point for $80AUD