amd64 or i386?

[Carl Brewer <carl%bl.echidna.id.au@localhost>]

I'm about to replace some aging hardware (2.8g celeron) with new stuff, 
Intel C2D E7400 with a swag of RAM etc.  The new motherboard has an 
ethernet chip not supported in 4.0.1 (realtek 8168B/8111B Rev 0.02) so 
I'm going to have to go to 5.0RC2 I guess or fiddle with unreleased 
kernels.  Anyway ... The gist of the question :

As I'll be pulling a number of apps over, including a cyrus mailserver, 
plone & zope, sendmail with some milters (clamav & spamassassin) and a 
few other bits & pieces including apache 2.2 and squirrelmail, should I 
go to an amd64 architecture or stick with i386?  This is by no means a 
criticism, but with OpenSolaris i386 stuff seems to 'just work' on 64 
bit systems as far as I can tell, is this the case also with NetBSD 5.0 
amd64 and i386 stuff (mainly from pkgsrc).

I guess the meat of it is, I expect to run this box as it is for 2-3 
years, is it worth going to amd64 or should I stick with i386 for ease 
of the move?

Any suggestions much appreciated!

Carl