I'm using the Linksys AM200, running the latest firmware. Rock-solid stability. Constantly running, with torrents downloading around 85-90% of the time. Great modem.
The router I'm using is the Linksys WRT610N. Unfortunately, considering your budget of 5k for both, this would be out of the question. I would suggest the Linksys WRT400N which is also a simultaneous dual band Wireless N router. Or even the WRT320N if you need gigabit ethernet ports.