> least double the memory. Is this a reasonable approach?

I have a dual 400MHz 2GB U2 and it is still a good machine (as
long as you can live without PCI).

I'd buy the maximum sized 128MB DIMMs (Sun Part no X7004A for
a kit consisting of 2 DIMMs).

There are four banks of four DIMMs and the memory must be installed
a bank at a time (i.e. two kits at a time). You should be able to buy the
kits
for under $100 US.

I upgraded my machine from dual 300MHz to dual 400MHz ( Sun part no
X1193A) and I think that it's worthwhile to do this. You just need to make
sure that you MOBO can support the highest spec CPUs;

http://sunsolve.sun.com/handbook_pub...z_UltraII.html

I paid $225 US per 400MHz CPU 18 months ago so you should probably be able
to source them for significantly less now.

In summary I would recommend loading one, or both of the machines up and
they should
serve you well.

HTH,
AT