If you have a linksys, you may be able to flash dd-wrt to it and this will support WPA in repeater mode. I have this exact setup:
Internet > Cable Modem > Linksys WRT54GL (Router - stock firmware), SSID: linksys > Linksys WAP54G (Access Point - dd-wrt v24), SSID: linksys1 > Dell Powerconnect 2716 port gigabit switch > More computers.
The link between the WAP54G and WRT54GL is WPA2 and the WAP54G is configured in repeater bridge mode i.e. it acts like a wireless ethernet bridge (driverless wireless for anything connected to the LAN port on the device) and WiFi repeated upstairs where signal is weak.