this project might be interesting to you. its a work in progress though.
if you want to do so with a non expensive router try DD-Wrt or OpenWrt and some linksys router (just check that it has more than 2mb flash or you will cut yourself trying to configure micro builds) :) its a regular linux box, fully configurable just the official firmware is very limited.
but remember not all connections can be spanned on all available WANs. (example : torrents will sky-rocket but you will have same ping in DotA :F )
if you want a professional solution i dont think its something you can explain via message :P at least idk how ^^