From what I saw from the manual, you can go up to ADSL2+ (24Mbps) with that modem/router. The only thing that I found really out of date was its wireless security: I didn't see WPA2 security...
I doubt that your router can dial 2 PPPoE connections OR 1 PPPoE with PPPoE Passthrough (aka PPPoE Relaying / Half-bridge) enabled. You would most likely have to set the router in 'RFC1483 Bridged' mode and dial both connections from your PC. Just note that when you have it in Bridged mode, you won't have ANY Internet UNLESS you dial a PPPoE account the attached network device.
I have that router for a couple of years now. It supports ADSL2+ and is capable of half bridge mode.
It does the job well and not planning to replace it anytime soon