your DIR615 will do you in the short term dude but you really need to be looking at a new router. Under no circumstances should you use the shub in router mode. If you want to do yourself the biggest favour ever and save yourself a great deal of time and hassel you will put it in modem mode and buy yourself a Linksys router. There are various models to choose from and what Craig has suggested above are the top of the range models which you might not need. It looks like they have changed the range about. Something like this should be perfect for you and is a bargain at £65 because it was £100 a couple of weeks ago when I recommened it to someone.
http://www.amazon.co.uk/Linksys-Perf...3435912&sr=8-4
Lots of features but the most important thing for you is that it has got gigabit ports and simultaneous dual band which is great. Run n and g at the same allowing all your laptops, mobile phones etc to get connected at their maximum speed.
I have always used Linksys routers from day 1 and never had a problem with any of them. They have always been rock solid, reliable and delivered great performance.