I used to use the TP Link load balancing router then switched to that Billion 7800N. All it can really offer is a failsafe if one connection fails, you wont get the benefit of combined speed of both connections. The variations in network latency between providers prevents data packets being split effectively over 2 connections, you will just end up with timeouts and packet drops. The QOS engine on the Billion is great, you can specify gaming/Voip to one connection then web browsing or even specific PC's to the the other connection (for example).
I use this at the moment, far more powerful...
http://www.broadbandbuyer.co.uk/Shop...ProductID=9299
It is possible, just rather pointless, time consuming and pointless for home use. If you enjoy tinkering with tech then go for it, but otherwise I would spend your cash on something else.