Do they want a Hi-Fi system or just something to play music??? ... For the HT, I agree that has to be something good, but What about for the rest of the house??
I have a dedicated room for my HT (small, but I enjoy it)
For the whole house I have a Sony STR DE510 (it cost around $200), I got a pair of speaker selectors at Radio Shack (around $50 ea) and seven pair of speakers (cheap, different brands) ... I really don't care about the performance of this system because is just to have music on the background
Is up to your parents to decide What they want ... you can do it with $2000, but don't expect a lot