It all depends on what you want to do with it - if you are happy to take a base unit and not do any major upgrades, then any of them are ok.
Can you hold on to your money till after christmas? - by then there will be some better deals available.
I keep an eye on the PCWorld clearance section and see a lot of e-machines and compaqs in them so would avoid them. Their own brand Advent machines can be good value at times.