32-bit vs. 64-bit Vista

Hi there,

I will be building a new Intel i7 "super computer" soon, with 6GB RAM
maybe (see below).
Up to now I have 2 desktop machines with Windows XP Pro and two
laptops with Windows Vista Home Premium !
I personally don't have any problem with Vista at all but in my new
build I am looking at either putting on Windows Vista Ultimate 32-bit
or 64-bit.

Basically what I need to know is is there any problems with using
64-bit Vista ? .. mainly I am wondering will all my "usual" programs
like Eudora (email), Agent (Newsgroup), Nero, Microsoft Money etc run
on it ?

Or will it be more trouble and money (because of having to re-purchase
64-bit programs) than it is worth ?
And in that case should I just settle for 3GB RAM, or buy the 6GB
anyway on case of future upgrades ?

Any help/advice would be greately appreciated !

Thanks in advance,

Steve