Remember, if the main house is using a capped account it wont work (well it will but let me explain),you can have 10x1Meg accounts on a 10 meg line should they all be limited to 1Meg.
But should you try log into your 2Meg account on their 4Meg speed it will clash and will ruin both connections.
So you need to ISOLATE it, if they have a 4Meg capped account you need to get hold of their ISP and tell them to limit the speed to 4Meg, then you upgrade the line to an 8Meg and run your 2/4Meg, but it must not exceed the current sync rate.