what's the best way to get Vista Ultimate, 64 bit?

I have a m1330. I have Vista Home Premium 32 bit.
I'm perfectly comfortable with this set up, but I'm wondering what could be the best way to upgrade the OS.
I'm thinking about Vista Ultimate because it has some cool features, like remote desktop.
I would have to buy the full version to get Ultimate, right? or could I buy the upgrade version?
If I understand correctly, there's no other way to get 64 bit, besides buying the retail box of Vista, correct?
The Vista alternative media thing doesn't work because this is OEM, and I don't want to buy the same OS (home premium) and then send in for the alternative media (64 bit). So basically the only option would be to get either the Vista Ultimate upgrade or full version, is this right? and if so, which one will work?
(the upgrade literature says upgrade from XP and 2000 etc, but nothing about Vista Home Premium)
(mind you, I'm not really too serious about this, Vista Home Premium is far and away good enough for me, and I have no need for 64 bit, I'm just wondering what options I have if I wanted to upgrade)

 

http://www.microsoft.com/windows/pr...orupgrade/windowsanytimeupgrade/overview.mspx

 

You can either get an upgrade or a full install disc. If you get the full install retail disc you get both 32 and 64 bit OS. You can upgrade from a full install disc which I did on mine. An upgrade disc is cheaper than buying the retail version and I believe you can clean install from an upgrade disc.

 

Or, buy the upgrade from Windows Anytime Upgrade, online, and once you've upgraded to 32-bit Ultimate, request a 64-bit DVD from Microsoft (or, I presume, you can borrow a friend's disc, since you would have a licensed copy of Vista Ultimate of your own); just save your CD key when you do the initial upgrade to Ultimate so you have it when you do the clean install of Ultimate 64-bit.