Hi,
This is a difficult one, it depends on three things really
1 What do you want it for
2 Is it for you or the kids
3 Do you want it for portability or space reasons.
I ask because if it is for the kids, then Macs aren't good news, in DT they all use PC's and adding a mac into the mix can be difficult. For some kids (they are usually better than us adults) it's not a worry, but the operating systems do differ.
If you just want it for office and internet then cheap and cheerful is usually OK. If you want it for gaming, then graphics and sound are an issue.
If you want it for graphics, photoshop and arty uses it has to be the mac.
Space issues, I know this will sound radical, but I have a compaq pressario, I bought it new 4-5 years ago and it is getting to the end of it's life now, won't play daughters SIMS game. But I am fortunate to have an electronics expert and computer geek hubby who keeps it going. (dont ask me how it's a black art).
It all depends on what you want really.
I have a super PC in the dining room with TV freeview box, wide screen etc, a Dell for work, my compaq (best investment ever) for internet, office etc., and my MAC for arty stuff.
Answer is give us an idea of the full capabilities you want from it and we might be able to come up with something that fits the bill.
Hope that helps
Jackie