Don't do it, I'm gonna go the other way soon, and I would not use Dell.
Not because of the lack of quality of product, although remember you'll be using Windows .. ... . . .. . . .. I'm just cleaning up another virus attack, even though I have Antivirus Firewall anti spy etcetcetc. But I was going to go with Dell before deciding to move, I contacted them and received dreadful Customer Service, I was treated pretty badly for someone who was going to buy a £1000 machine, I have sent lots of emails looking for a response and received nothing.
I know I'm 1 in a many million, but you wanted a response, why don't you hang on until Leopard and if that doesn't live up to expectations, you can spend more money and go to the wonderful world of, oh no I need to update my virus database, ahh I've got some spyware, why has it crashed again.
Hey other than that I love windows........